You are right. Buck has no problem publicly calling out kids in the minors or rookies but if he does talk to his vets it is in such a way to help shield them from outside scrutiny.
Me, I think that if calling Mountcastle out in public is a good idea than maybe calling Davis out in public for his called third strike issue might be a good idea as well.
So yea, I think he should afford all his players the same level of respect.