Recently, I have gone through a spate of unpleasant incidents with different individuals in diverse venues that all had something in common. Some disagreement turned into violations of social etiquette--or at best missing the point--that quickly devolved into hostility. My recent response is to block that discussion so that I can no longer see what is going on and thereby not be tempted to "Feed the Beast!" Hence, I offer the procedures that I try to follow to avoid accidentally antagonizing interlocutors when discussing philosophy online, which by its nature elicits argument and disagreement.
1. Our words always have unintended meanings that others may grasp: some of these unintended meanings may be true without our awareness. I might be an unwitting jerk in conversation, for instance. The problem happens when someone calls that person out as a jerk, etc., which is very likely to produce the unwanted behavior whether it was previously true or not. In short, an accusation often produces the behavior: do not accuse. By the time you, or I, make an accusation,we must accept that we are picking a fight. Refuse to accept this, and you are in fact a jerk.
question rather than accuse
2. Ask questions and for clarification. I always try to do this, and I always think I could do it better. Rather than accuse or assert, ask the person if they intended to communicate what you are tempted to accuse them of. This may avoid a confrontation, although some interlocutors will treat a question as the same as an accusation. I suspect that I get in trouble on this point a lot, and the best advice I can give is to do it better than I do.
when to exit
3. If derogatory language starts flying, that's the sign to get out now! Nothing productive will occur after that.
pro-actively preventing conflict
4. Try not only to treat everyone in a friendly manner, but do your best to feel like a friend. Online media tend to elicit fast and strong emotional reactions, and one way to counter this is to pro-actively establish a positive emotional attitude towards your interlocutors.
be mindful of your audience
5. If you say anything negative about a group of people, presume that at least one member of that group is in the audience. This trick either keeps you in check from saying anything too harsh, or reminds you that you are intentionally provoking someone. Yeah, I say negative points all the time, but this tip is to avoid accidentally doing so. I don't know how many times I've heard someone disparage academics or philosophers in a conversation … and then don't seem to realize they have offered an insult. Likewise, I'm mindful when and where I work my hobby-horses. (I'm particularly harsh to mainstream analytic philosophy.)
Of course, I would love to hear counter-points to any of these and other suggestions. Given my experience, I'm convinced that some conversational styles cause conflict that the interlocutors attribute to ill-will. I have run into plenty of people that, at least at first, appear to be a problematic conversant, whereas I later discover that two-thirds of the problem is how they approach conversations (see the previous point) and the last third is just bad conversational habits.