Yes we don't know bajaj's reason. But do u think it has got anything to do with Anupre? Have they personally wronged him? No! Somebody else has wronged him. Anupre toh r still coming out of their safe cocoons, how would they wrong him? N if they haven't done anything, why should he extract someone else's revenge from them? Hence I don't find him grey. Till now, I haven't found a single white thing about him that will make him grey from black, forget anupre from the picture even. Even if it is typically like bajaj is Moloy's long lost son n moloy accepted Anurag n kept bajaj deprived of fatherly love, I don't support a full grown man like bajaj to take revenge from Anu. Anyways, let's wait for the revelation of his past.
N I believe when u love someone, u accept them completely. U accept them in the times of happiness n difficulties as well. Yes, it doesn't give the other one a right to humiliate u, but u too don't trust the face value easily. When in love, u give the other person some right upon u with which he can take some liberties n it is not a weakness according to me. Well that's my opinion only.
Bajaj works on Domino effect. Prerna is target because Anu will be hurt. Anu is target because Senior Basus will be beyond hurt. As said earlier, secret is the only thing keeping him on the hook right now.