I would be hesitant to openly mock such people
I think the very fact that we’re even having this discussion is an excellent reason to openly mock such people. I would be more inclined to leave a private person alone, but when someone openly declares himself an Orthodox Rabbi, and openly spews apikorsus, he and his views need to be openly mocked, not despite, but particularly because, someone like you can come along and even partially defend him and his views.
If I have time later, I will try to (again) address the second point.