I happen to hate the phrase "Devil's advocate." I apologize for giving offense.
It's clear to me, given where the first-hand accounts are coming from (a respected member of the SF community, a woman who was touched inappropriately by Ellison the same weekend, an account of wrangling Ellison at the Hugos, and a since-removed photograph of the grope), that the grope happened, it happened on-stage, people saw it, at least one person got a picture, and Ellison was behaving badly even by his own generous self-set standards.
Maybe you've not seen any of those accounts, which makes your wanting the other side understandable. If you have, then all I can do is boggle.