The GOP is not responsible for the White Nationalist types, for instance. There are always going to be fringe elements.
But the president sets the tone. And we have never - ever - seen anything like what Trump says at each of these rallies. You should watch them, if you haven't.
This is not a partisan issue - Bush was never like this, and neither was Reagan. This is a decorum issue.
If your whole political strategy involves appealing to the worst instincts of your base and rousing the rabble, you can't be surprised when some of that rabble is roused in dangerous ways.