Johnny Manziel Defends Jimmy Garoppolo, Let Him Date Porn Stars!!

Johnny Manziel says Jimmy Garoppolo's date with a porn star is no big deal ... and hooking up with Kiara Mia could actually make the Niners superstar a BETTER quarterback!!

The new Montreal Alouettes QB addressed the hot topic on his "Comeback SZN" podcast with Barstool Sports on Thursday ... saying people shouldn't worry about his dating life as long as he's winning games.

"What's wrong with it?," Johnny says. "Dude, let the guy live his life! So what, what she does for a living?"

"If anything, that's going to make him play better on a Sunday or a Monday."

Johnny even sends a personal message to J.G. about the date ... saying, "Jimmy G, live your life! Do whatever you want."

"He's backing it up on the field, he hasn't lost a game. Nothing. Guy's doing everything... and he's enjoying life. So be it.

As for Jimmy ... he finally addressed our story at training camp on Wednesday, calling the date "a good learning experience."