There is no immunity but there may be a political price to be paid for the way Donald Trump went about it. Time and the polls will tell whether more Republican primary voters agree with him or disagree with him
McCain is a sideshow and the issue will be overcome very soon by far more important topics of discussion
From what I am reading many many vets are just fine with the Donald saying what he thinks. With any luck he has widened the opening for the “ untouchable” McCain to be primaried out at the next opportunity