I've been around the Internet for quite some time, so a topic like this is nothing new, and I mean no offense when I say, "Welcome to the Internet," when someone talks about trolls/flaming, etc.
I do have a few things to add:
a- Don't bring "anonymity vs real life" into this without really going into that topic. Some of us prefer our anonymity regardless of our actions. Even if it is tenuous. I'm not sure I've seen 5 people on this forum with their real name in their username/signature. :P I would rather have a$$holes and anonymity online than no anonymity and everyone being happy and shiny.
b- It is very, very difficult to criticize someone else and not come across as a troll oneself. Especially when one begins to make assumptions on their life, situation, attitude, insecurity, etc.
c- Just because someone disagrees with you, doesn't mean they're flaming you. This is very often forgotten, especially when you get into passionate topics like politics, ethics, religion, even our hobbies. Many things are read between the lines, including tone. Conversation in text can also be a matter of perspective. What is inflamatory to one person is normal to another. We need to have as much thick skin as thin skin... For instance, would one consider this particular post a flame, or not?
d- Sometimes someone needs to say the bold thing. If you're doing something dumb, someone needs to smack you upside the head and say settle down. Some of the best discussions occur when we're standing up firmly with our opinions/statements. Some of my best friends/social interactions have started out as disagreements of some sort. And that's speaking IRL, not on the Internet.
e- Not everyone is a good communicator when it comes to text. That's just how it is, which means sometimes things can be read wrong and others can come across as more abrasive than they really intend.
When I'm at the bar, and some redneck is being an ******* in the corner, I don't go up to them and plead with them to be civil, or go to my corner off to the side and try to get people on my side. People can be how they want. If they cross the line of the establishment, then they can be removed. But until then, we have to tolerate the various behaviors up to that line.
Lastly, if someone is an a$$ in a thread and you think a post went over the line or at least wasn't necessary, post a response in that thread and say, "Lighten up, man." Just like you would in a social interaction where you pat your bud on the back and say, "Lighten up, man, that wasn't necessary."