They're probably booing him because trump doesn't like him, not because of any specific policies. Most of the simpletons in the audience work off emotion, not logic.
And also hilarious, since he was all too happy to fully enable Trump.
All that power that he cheated our democracy to put in Trumps hands, so that he could use him as a puppet to further his far right agenda, has turned on him. Even after kissing the ring after falling in line again after a very brief "perhaps we've gone too far" moment on Jan 6th.
Fuck you, Mitch. You destroyed our democracy. You did this. You raised an idiot to a dictatorship thinking you could control him. Great fucking job.
As is tradition. A lot of the more "moderates" in Germany thought they could easily control Hitler. Idiots failing to grasp weaponized stupidity in the hands of other idiots.