I was revisiting this old thread today, when staring at some more one-sided Facebook comments from my "friends." Nothing's really changed in the political world and nothing's really changed in the online world.
To the extent that my own behavior has changed, I've adopted a new rule for myself. If all the discussion is one sided and I'm the only guy on the other side, then it's not worth my time. If others chime in and something resembling a debate emerges, then it's more fun to stick around and be part of it. Also, I've conceded that there are some people, like the fellow who I quoted at the top of this thread, that I just don't bother engaging with, while there are others who are just as strident but far more fun. They'll drag concessions out of you and you out of them without either side descending into ad hominem attacks.
My least favorite debating tactic that I've ran into in this world would be the "mushy ball of entangled arguments" -- hundreds of words, in a single paragraph, offering several disparate arguments toward an inconclusive point. If you attempt to tease out the individual arguments for discussion, you get back another mushy ball. For those, I hereby surrender.
(EDIT: fixed grammar issue after seeing it quoted below... sigh.)