It's not on camera and he claims he didn't do it. He said some disrespectful stuff about McCain in the past, but they also had a personal beef due to McCain dissing Trump publicly. I have to admit it seems like a rather strange thing to say out loud even for Trump, and it's a little suspicious that it surfaced right before the election. I'm not saying he definitely did or didn't say it, but my bullshit alarm is definitely whirring on this one.
It's not just McCain. (by the way, the McCain stuff WOULD be bad enough on it's own)
It's what he's said about various flag officers, even ones who have been on his own cabinet.
It's what he's said about his brother Fred who joined the Air National Guard.
It was his callousness when talking to the widow of Sgt. LaDavid Johnson ("He knew what he signed up for". Johnson's wife was in tears.)
The fact was, he DIDN'T go to the ceremony at Belleau Wood.
Trump's long history has been one of disrespecting people who intimidate him, who he feels threatened by. The guy is by any definition just an awful person.
He's a guy who reacts to 180,000 Covid deaths with "It is what it is!" He simply lacks the basic human empathy most decent people have.