You are correct. Trump is making fun of some reporter's neurological disability. Apparently that's funny.
Maybe. Maybe not. If he was, then it was great because that reporter was a liar and a goon. He moved next door to Palin so he could ostensibly snoop on her family while at the same time intimidate her.
That ahole reporter should be savaged, but we all knowbthe Cruznadians love him long time.