Online media attempt to amplify these differences to the point of rage because there's money it in.
As we have pretty strong social expectations for how people behave at meals.
It is common these days for people to interpret the self-management people perform as a type of filtering (or "hiding" in your words). I find the cynicism in this viewpoint to be distasteful, when equally one could interpret the same behavior much more favorably.
When someone, for example, tidies their apartment because they anticipate a guest, they are engaging in exactly the same thing. But this is widely considered a good thing. The connections one anticipates have caused one to "brush up". The same thing is true for outspoken opinions. We aren't just "real" creatures with disgusting opinions walking around wearing "fake" masks to hide them.
The treatment of a person is different depending on which lens you opt for. On the one hand, you view society as a collection of people who ought to be unmasked, for their true identity to be uncovered and scorned appropriately. On the other, you view society as a collection of people with a fluid set of opinions that are molded by the company they are with. The unspoken idea becomes the forgotten, abandoned idea.
This is more like having kidnapped people in your house and hiding them so when someone comes over for dinner, no one can see them. I'm not morally opposed to a cluttered counter.
I think the difference in our positions is that you think people are born with a rigid, unchangeable "real" opinion, and I think opinions change according to the person's company.
But I think avoiding political conversations is best described by what I've seen called "social cooling" - I don't really care about litigating morality with family at Thanksgiving. We may have fundamental differences in our interpretation of reality and human behavior, but that doesn't make one of us an actual criminal.
“Well, yes…”
“What have I said about talking about politics with people I love?”
“That you don’t.”
(Looking very forward to a frank conversation with my dad about his apparent need to keep a loaded handgun in his nightstand before we bring our toddler to visit, by which I mean, “actively dreading”)
Put someone in an environment where social norms favor civility and respect, and they will generally become more civil and respectful over time. Put them in an environment where social norms favor tribalism and vitriol, and they will tend to become more tribal and vitriolic over time.
That said, I think we should be cautious about nostalgia for how things worked before the Internet. 30 years ago, people in socioeconomically homogenous communities might have been adept at being civil to and empathizing with their neighbors, but they perhaps also had a lot less opportunity to become aware of what was going on outside their bubbles.
Cars are an interesting in-between, where we're just barely removed from being in-person and as a result we tend to act far more rudely and dangerously than we would to someone's face.
But remove the physical proximity and the vitriol often re-animates.