As often is the case, the disagreement seems to boil down to simple miscommunication. If I'm right in my (somewhat cursory) assessment, then there's no actual difference of opinion, and this is just yet another mundane example of the words getting in the way.

There is a difference in actual opinion. It is not excessively important right now given how little power we have over this scenario. It would become important if we were, for example, choosing where the law should place the boundary of 'libel' and related laws.

He argued that they aren't targeting somebody they think is innocent (thus they're not "evil"), and that their failure of irrationality was understandable (therefore not "disgraceful"). That's it.

That's a big 'it'. I understand why humans do an awful lot of the things they do and quite often empathize with them. It's understandable for people to want other people's stuff, have sex and to eliminate rivals, for example. That doesn't make the behaviours involved less disgraceful or necessary to prevent.

So what's the difference? He seems to have pinpointed the former term as implying that they're trying to do harm, and the latter one as adding a whole slew of extra layers of incompetence or idiocy.

They are trying to do harm. They are trying to destroy the lives of some scapegoats.