The supposition that the heckler was not fully mentally capable does not appear to be backed by any evidence. As such is it a somewhat disgraceful discriminatory assumption - a prejudice.

Lots of people throughout history have been accused of such a thing and been detained, imprisioned and killed on little or no evidence. It still seems to remain a useful accusation to use against anyone brave (or foolish) enough to express a different view.

Sometimes it would appear to be a duty for some - to join in with these cries and to be seen to jump on this bandwagon - rather than being seen for the unworthy expression of group prejudice that such accusations clearly are.