Don Lemon is torn over Megyn Kelly's controversial interview with radio host Alex Jones -- but ultimately seems to think he's not worth the airtime.

We got the CNN anchor at LAX and asked what he thought about the backlash against Megyn for interviewing the Infowars host ... who's theorized the Sandy Hook massacre was a hoax.

Some parents of victims are blasting Megyn, and lobbying NBC to yank the interview. Don, at first, had Megyn's back ... saying sometimes journalists have to go to "dark places."

On a personal level though ... Don dismisses Jones as a total phony who doesn't deserve a platform.