You can't add a disclaimer "Don't interpret my words as aggressive"

Well, you can often interpret someone's words many ways. Just because you cannot see the person, and you cannot get information about their emotional state. So, i think you can write something that can be understood many ways, and add a disclaimer, "it's not the other thing".

Regarding

using excessive familiarity with an opponent is a type of insult

I never saw this. Maybe we are from different areas, and this could be explained through cultural difference. First, I am thought to never approach opponent as an enemy, and to always keep in mind they are like me (meaning they are humans, with feelings, with ideas, with goals, with hobbies, with experiences) and not empty, emotionless, evil, etc. Furthermore, I approach discussion as a cooperative activity, since its purpose is to improve both me and the guy I discuss with, and give us both insight in something new. That's why I never saw "familiarity" being looked upon, since that behavior highlights those two mindsets.

However, I acknowledge there are people with different background, who have different approach (different, not opposite). And now I acknowledge some people could perceive familiarity as insult. Would you mind explaining me how does that insult work? I don't even have a feeling for it. The closest I ever encountered was where middle-high-class-old-lady meets some homeless person who says something along the lines of "we are the same" and then she stops him to say they are not the same, etc, but that is pretty far from this case.

Edit: formatting and spelling.