It only implies "objectively wrong" if you believe in objective morality. But even if you do, the term "evil" also implies that your top goals and theirs conflict, so it works even then. The alternative, it seems, is to have "evil" be a term we can't use under any circumstances, which just means some other word or phrase will come to mean what "evil" meant before we stopped using it, and it looks like you're using "alien" for that purpose in the other branch of this thread.

The 19 hijackers (or Hitler, as originally mentioned) were not (necessarily) irrational, stupid, insane, or otherwise mentally damaged. Nor were their motivations completely opaque or untranslatable, as "alien" implies -- any human could understand their position given the effort to do so, unpleasant though it might be. Their goals were just incompatible with our goals, and only one set of goals could win. It seems to me that evil is exactly what that means.