The tongue in cheek term for this is "JAQing off". JAQ = Just Asking Questions. It is also known as "concern trolling". Any fool who spends the effort to successfully address the face value concern will find that the troll has immediately transitioned to having a new concern which happens to support/oppose the same exact things as the previous. It is a textbook example of motivated reasoning laundering itself in the clothing of skepticism.

It is like fighting a squid. The moment you've caught it by one of the tentacles it slaps at you with the other 7 while the first 1 slips away.