I suppose that “fat pig” is not in Donald Trump’s lexicon of insults, but “liar” is? While Rosie may be fat, she is not, in a literal sense, a pig. McConnell lied, so he is a liar, thus Cruz made a statement of fact, not an insult.
(Not that I disagree with, or object to, his characterization of Rosie O’Donnell, mind you.)
Yes, Rosie is a fat pig but saying that is in questionable taste if one is running for president.