Macho Mel Gibson exploded and lashed out at Richard Chamberlain after the out-of-the-closet actor made a snide comment during his “Yep, I’m gay” TV chat with Katie Couric — hinting that ultraconservative, religious family man Mel might have secrets to hide! Talking about his decades-long double life as a closeted homosexual, Chamberlain suddenly blurted: “I mean, Mel Gibson, for instance . . . who knows who he really is?” Gibson’s FURIOUS! He believes the crack was a sly insinuation HE might be gay — a weird irony, considering he’s often been accused of homophobia by gay rights groups! Seething, the superstar fired off a letter — blasting Chamberlain for dragging his good name into “your sordid life!” AND warned him never to use his name again! No response from Chamberlain so far, but . . . stay tuned.