Trump says, during this interview with Fox News today, (he has a point here) that John McCain called Trump supporters "crazies" after a rally last week in McCain's home state of Arizona. The actual quote was, Trump "fired up the crazies." Donald Trump tells the Fox Panel that McCain insulted his supporters, and he is insulting him back.
Trump clearly could have went after McCain on a different issue than the POW story, but Trump, angered by McCain's comment, punched back yesterday in Iowa
Listen to the interview he gave with FOX