I dunno. It's never black & white is it?
I have an old mate on my fb who is basically a decent fella but does come out with some outrageous shit - mostly to provoke debate - but I enjoy the comments other people make to shoot down his positions. So does he.
Although he does have some nasty tory mates who post their reactionary shite too. But it's all done, mostly, in the spirit of canteen/gym banter (he is a Plasterer and a Martial Artist). But if I - and the couple of Anarchist Martial Artists who also post - delete him, then we abandon the field to the reactionaries.
Interesting points you raise there, Liam. My own "rules" for FB is to allow discussion/debate etc to be as open as possible, and if I have a fundamental disagreement with someone, then the best way is to argue the case on yer own side. A couple of days ago, I got into a debate with a real-life friend on FB re politics and anti-fascism - their view was that all politics is essentially useless and not worth bothering with, and that political activism changes absolutely nothing. I didn't agree, but was calm, polite and stuck to the facts. We agreed to disagree in the end, and finished on good terms.
On the other hand, I found out that a "name" music writer is on FB these days, and this is someone I've known on and off on an offline level since 1993. For reasons best known to themselves, they've become a rather major suppoter of black metal - a genre of music I overall absolutely despise, due to the political "thinking" of many of the groups involved in said genre (the musical "merits" of black metal is something I'm supremely uninterested in these days - I did have an interest in some of the groups involved 6 years ago or so, but alarm bells started going off in a big way once I read "Lords Of Chaos"*, and once I read up more on this, I dumped the whole thing from my life....the only band that I have even the smallest time for in that scene is the Japanese band Gallhammer, who are far more crust-punk than anything, and are a very rare case of a black metal groups without rancid politics). Anyway, I was momentarily tempted to hook up with them on FB, but decided against it - they've stuck to their guns on black metal, in spite of the overwhelming evidence of the amount of political garbage involved in that scene, and I concluded that I'd only get into an immediate argument with them, which would be totally futile and energy-wasting. It's sad really, in a way, because before that they were perfectly decent and reasonable, but I have a hard line on fascist music, and I'm afraid to say anyone who defends that scene is beyond help to me. Maybe that's unfair, maybe I should listen to what they have to say...but to be honest, I think you have to take a stand somewhere along the line, and say "no, this is unacceptable", and that's my own personal line.
(*Later on, I found out that one of the co-authors of "Lords Of Chaos" - Michael Moynihan - is a major league fascist himself, and the other co-author - Didrik Soderlind - has made positive noises towards the anti-immigration Swedish Democrats. No wonder the book contained not one instance of any repulsive views being challenged).
2 years ago, I also found to my horror that 5 (five) FB friends also had a certain Mr Southgate as their friend there. At the time, I thought, "Jesus Christ!", and binned them all immediately. Would I do the same today? Depends - if I knew them offline, I'd approach them directly and say "what the fuck is this all about?", and try to persuade them to cut ties with someone like that before ending a relationship with them. If I didn't know them personally, then the banhammer would come out again, I'm afraid. I'm also dealing with 2 FB friends who have "liked" the official David Icke page there....again, the banhammer might be coming out there too, as our discussions seem to be getting not very far at all).
I think, ultimately, you have to take contentious issues on a case by case basis. Argue and debate and challenge where you can, but reserve the right to cut ties where necessary. And sometimes, you have to be brutal and swift in cutting ties as well.
Hope that makes some sort of sense! Be interested to know what you make on my take on things.
P.S. Just remembered this - I also fell out both on FB and in real life w/the former singer of the Stretchheads, after I found out about his real-life friendship with Douglas Pearce (Death In June).