There is not a guide, and I think you understand the difficulty in creating such a guide. However, applying labels to people or making assumptions about them, is not necessary, and may offend. And part of the problem is the 'tit-for-tat' that such things often prompt, which can easily spiral into insults and slanging.
For example, calling someone a lefty or a liberal may prompt responding with calling someone right-wing. None of the terms are ones that will necessarily offend, but they can be used dismissively, or derogatorily, and someone who feels they are centrist or left-leaning may well be insulted by being called right-wing. The problem is exacerbated when people add emotive labels, like 'bleeding heart', 'virtue signalling', 'xenophobic', etc. These things are unnecessary, don't contribute to discussion, and generally get people wound up. That sort of thing was perpetually a problem with the Brexit thread.
When people push the boundaries of politeness to make a point, or feel they gotten one up on someone, they really need to reconsider if there isn't a way to phrase things that are less likely to prompt an irritated repartee, or insults in return. Or maybe just not post on that topic for a bit.
Those who do not find the above to be enough of a 'clue' should, perhaps, reconsider whether this forum is the place for them.