Marcellus Wiley is all for Jimmy Garoppolo dating porn stars ... and he doesn't care if the QB's marketability takes a hit -- telling TMZ Sports, "I think he's made enough money, he doesn't need every damn endorsement!"
We got the ex-NFL star out at Equinox and he told us, because of Jimmy G's new $137.5 MILLION contract ... he can afford to do things like take the star of "Bra Busters 4" on a VERY public date.
"He made $137 million off of seven games, do you need Pepsi too?!" Wiley tells us.
Marcellus then goes on to explain since everyone consumes porn ... there's nothing wrong with the Niners quarterback taking his affinity for it to the public space!!