You are blaming Trump for calling out the GOP because it will hurt the GOP. Why do you not similarly call out the GOP for causing the issue in the first place?
Similarly, why do you not also identify the "Never Trump" movement in the GOP as being equally damaging, should Trump get the nomination, and only slightly less damaging if he does not?
If Trump wants to call out specific members of the "NeverTrump" movement for being in that movement, I have no problem with that, although I still think that is a stupid move tactically.
My objection is that his broadside smear of "the Republican Party" -- which is exactly how he has phrased it -- punishes a whole bunch of people who had nothing to do with what he is mad about.
His mouth runs away with his emotions, and his brain apparently is insufficiently disciplined to keep it in check.