Should the fact that he didn't defend himself be ignored or counted against him?
If he was told that he had to answer his case on the forum, then not ignored. If he would have had to check the forum to realise he was in trouble, ignored.
Should the number of such accusations made be weighted it (I think I read he sent more accusations than the single one reported?)?
I think so, yes. If I steal two items from a shop, they don't decide to only charge me for one because I "didn't know" stealing was a crime.