So if a scholar is also a marxist-leninist and teaches at an university they are automatically intelligentsia? Even if they support ML/Communist ideas?

I assume it works like the Engels situation. He was part of the bourgeoisie, but acted like a class traitor as far as I understand.

So, that professor imo would be part of the intelligentsia, but, if he actually teaches ML ideas, acts as a "traitor". In this case, unlike Engels, the professor is not part of a different class and exists more as a faulty tool than a class traitor.

Take this answer with a grain of salt though.

I am not yet educated enough to even attempt to answer your second question😇