[MrB]

In other words, leftists never argue based on the merits of the issues and concerns being raised, because they can’t.

Instead they attack their opponents as illegitimate, intellectually/morally inferior, or, in the case of their prototype communist template country, USSR, classify opposition as “insane”.

[andy58-in-nh]

Leftists are not at all incapable of intellectual argumentation; they do it all the time - just don't challenge them.

Because if you, as a conservative attempt to point out logical fallacies, unsubstantiated claims, erroneous assumptions or false premises, they will not attempt to counter your argument. Instead, they'll call you a name and accuse you of something.