At least we can say that if Noam Chomsky does it, it must be OK for others to do it regardless of the fact that he says it is not OK.

Why should that follow? Why can't we say he's right when he says that, and wrong if he does that?

One way and another I suspect that all of us have in our time done things we have thought were wrong. In fact anyone who says they haven't is almost certainly a liar.