I think it's up to the women assaulted (and you're right; it is assault) to decide if they want to press charges.

I think it's up to us as a community to say "This pattern of behavior is not amusing, and will not result in praise but rather censure."

the F/SF community seems to have tolerated a _lot_ of outright illegal behavior at Cons through the years

Indeed we have.

And I think it's bloody well time we stopped.

I also study martial arts. What he did to me was rude, piggish, and totally inappropriate, but did not merit the type of response you mention-- especially since he's an old man, which does not excuse his behavior but would give me pause before doing anything to him that might break his possibly fragile bones. I suspect he trades on people's reluctance to strike an elderly person, which is obnoxious of him, but I would still feel that reluctance.

If he'd grabbed my breast, that would have been a more serious assault, and I would see a takedown or a knee to the groin as an appropriate response, no matter how old he is.

That being said, the burden should not be on women to have to defend themselves after they've already been groped. If Harlan Ellison cannot control himself, he should not be invited to conventions.