Conor McGregor took a giant dump on the UFC and MMA -- so says Bruce Buffer, who's sick to his stomach over the Irishman's violent bus attack.
We got the legendary Octagon announcer after he had a few days to stew on McGregor's window-smashin' rampage ... and he wasn't about to let Conor off the hook.
"It's an insult, it's disgusting," Buffer told TMZ Sports.
"In my 22-plus years of being in the UFC and doing everything I can in my life to build this great brand, to support this fantastic sport .