Trump is a democrat. He is in this race to do many things. Wreck Walker's future, neuter Jeb, belittle Rubio, and paint cruz as canadian.
He's also in the business of hurting the GOP. Terrorizing their delegates - which is exactly what we see here - is part of that.
Repubs had 9 months of George Will and other screaming Trump was a plant - they ignored it. Now they are going to have this trash going on at conventions thanks to their blind lust for his tv stardom and of course, his venom.