Maybe you've heard of radical honesty, or radical kindness (I think my favorite quote from Scaughdt Iam is "many of the platitudes that most of us still take for granted actually function exactly as they are written - with no exceptions whatsoever!"). I tend to favor radical kindness (as explained by Scaughdt Iam and Peace Pilgrim). And while I think dishonesty in personal relationships is almost always bad, I don't think silence is necessarily dishonest, nor do I think people have an obligation to volunteer honest opinions unsolicited (that is: to say everything on their mind as soon as it comes into their mind). My take on honesty ("radical" or otherwise), is that everyone should strive to be the sort of person whose thoughts would not surprise his/her friends, nor lower their opinion of him/her. In this spirit, I offer you the concept of "Radical Tolerance" as a step towards honesty and radical kindness. If a person thinks in a way that is radically tolerant, it will be easier for him/her to speak honestly (what could a tolerant person possibly have to hide?), and to act kindly.
Like many other moral philosophies, such as Homaranism and preference utilitarianism, radical tolerance is closely related to the "Golden Rule": the idea that we should treat others as they want to be treated. I think of radical tolerance not so much as a restatement of the Golden Rule or an alternative to it, but as a technology by which the Golden Rule is implemented. Someone following radical tolerance will tend to treat others as those others want to be treated.
The essence of radical tolerance is "the only thing that's acceptable to be intolerant of is
intolerance" (my phrasing, but I'm certainly not the first person to think about this issue), which I think is one of those platitudes that functions exactly as written with no exceptions whatsoever (at least not if you can find a perfect definition of "intolerance", which is the tricky part). Radical tolerance means accepting people for who they are and not asking (or even wanting) other people to change the benign aspects of their appearance, behavior, or beliefs. At the same time, it means standing in opposition, whether by thought, word, or action, to intolerant appearance, behavior, and beliefs.
From the perspective of radical tolerance, there is a moral value to aesthetic opinions. I've previously written a bit about prejudice against female leg hair, which I think is a particularly obvious and egregious example of intolerance towards something harmless. To think negatively about any healthy human phenotype is a breach of tolerance, whether it be height, weight, color, degree of glabrousness, or whatever. Perhaps negative thoughts about certain unhealthy human phenotypes are also breaches of tolerance; I'm interested in seeing discussion on that point (though that's not to say I'm not interested in seeing discussion on other points).
Behavior tolerance is probably the easiest of the three kinds of tolerance to understand and support. Tolerance of behavior just means that if someone else's behavior isn't harming other people, then don't worry about it. That is, if someone chooses to use drugs, or alcohol, or engage in consensual homosexuality (or any other consensual sex act), or whatever they choose to do, if their choice is not directly harming other people, then we should not get in their way, or even think less of them for it. Getting high or drunk privately at home (or even in public if you can behave yourself) is ok, doing so while driving is not. I am unsure of the extent to which we should tolerate self-destructive behavior. Certainly if a friend is descending into alcoholism, we should not just sit by and watch, but I think that we should also be careful not to judge too harshly. No one behaves in an optimally healthy, or optimally socially responsible way, and as long as their heart is in the right place, it's not fair to expect anyone to.
Tolerance of beliefs does not mean that we have to accept everyone's beliefs as true. What it means is that we should not persecute or think less of people for their harmlessly eccentric opinions. If someone believes that Santa Claus climbs down their chimney to deliver them presents every Christmas, that's ok, as long as they don't take it upon themselves to punish the unbelievers, or declare that unbelievers are somehow inferior. Similarly for religious or political doctrines, or whatever other topics people might have strong opinions about: insofar as those opinions are tolerant, they should be respected, though not necessarily agreed with. That's not to say that people should refrain from debating politics, religion, and other contentious topics, only that such discussions should be as respectful and impersonal as possible. It's ok to think that society would be better off if people tended to be more right-wing, left-wing, religious, non-religious, etc. It's not ok to pick out individual friends, family members, etc, and think "I wish they were different" (unless by different, you mean more tolerant).
Perhaps for something with name like "Radical Tolerance", this set of ideas will strike some people as ironically and harshly intolerant. However, it is important to realize that there is a huge difference between the intolerance perpetrated by people such as violent nationalists and religious extremists, and the intolerance perpetrated by people who think there is a correlation between attractiveness and body mass index. I think that the proper response to intolerance is proportional to the threat posed by the intolerance. Which responses to intolerance are appropriate for which situations is a field ripe for discussion. It may be that bullets are an appropriate tool for fighting terrorism, but I don't think any sane person would advocate the use of bullets to fight body shaming.
Here's an example of how radical tolerance can be applied in real-world ideological conflicts:
There are conflicts in the ideologies of atheism and
traditional Christianity that make it incredibly difficult for these topics to
be discussed among loved ones with opposite opinions. The really tragic part is
that the conflict is caused by generosity, thoughtfulness and unselfishness,
whereas almost all other interpersonal conflict is caused by the opposite. Both
sides desperately want what's best for the other side, and both sides want
nothing more than for the other side to change some fundamental part of their
identity (a change that is, in most cases, exceedingly unlikely to ever occur).
So these types of discussions are essentially exercises in selfless desperate
frustration. I can only imagine one possible solution to the situation. The
solution is to incorporate radical tolerance into our belief systems. In other words: to be tolerant of everyone else’s belief systems except for the
aspects of those belief systems that are intolerant of other belief systems. From that perspective, it's ok for an atheist to rail against the
horrifically intolerant idea that non-Christians will burn forever, but not
against the idea that there is a loving God making positive interventions in
people’s lives. And it's ok for religious people to be intolerant of the
tendency for some atheists to think that Christianity and ignorance are
synonyms, but it's not ok for religious people to think that a lack of belief
in God is a flaw in and of itself. Even this superficially benign suggestion to
solve our differences with tolerance suffers from the same fatal flaw as every
other solution: it requires people to fundamentally alter their ideologies. Insofar as New Atheism is anti-theistic, I would argue that it is a flawed movement and that its adherents should drop the blindly anti-theistic aspects of their ideology. In the same way, insofar as Christianity (or any other religion or philosophy) views things like non-belief or consensual homosexuality as flaws that should be punished (whether in life or afterlife), Christianity is a flawed movement and it would be better for all of us if Christians dropped the intolerant aspects of their ideology.