President Donald Trump is always eager to insult his perceived rivals, often with degrading nicknames, indiscriminate of party.

These past few days in London at a NATO summit were no different. He called House Intelligence Committee Chairman Adam Schiff (D-CA), who isn't present at the summit, a "a maniac," "a deranged human being," and "a very sick man" who "lies."

Trump is proving once again, however, that he can't take what he dishes out.