What I don't understand is, if your friend said that her husband beat her, you would support her.
I've never heard anyone read about a mugging and say "oh, but it might not have happened, I won't believe them until it's gone to court... anything else is damaging to the defendant's right to a fair trial".
On the evidence of that fucking horrible thread, I would suggest that there are one or two of the posters on there who probably would doubt those 2 scenarios. In fact, didn't the most infamous of them actually say that she would doubt someone saying they had been robbed because she knew someone who had lied about a burglary for the insurance? Might have been one of the others, but, jeez, what horrible people she knows, all those people who lie about being victims of crime!
Sometimes I think that MN is quite a wonderful feministy space, and then you have a thread like that, and realise that there is a hard core of women who really, and I mean seriously, hate other women. I almost feel sorry for them, they miss out on wonderful friendships, and then I stop, because they really don't deserve them.