Oh - could this be the best XKCD ever?
hhhhhhmmmmmm...well the competition for 'best ever' is tough. But this cartoon rings true to me.
Not about everyone I've ever argued with, but for a certain type of internet adversary (hello Neal are you still out there?). These people infuriate you at first but, while you may never end up agreeing with them, at some point in time, through some mysterious mechanism, you end up realising that they're just another person like you. With different - mistaken! - beliefs, certainly. But also with their own fears and hopes, cruelnesses and kindnesses, and all those other shared things that get lost in between servers.
Once you realise this it's much harder to be ruder to someone online than you would be in person...