UFC super-fan Travis Barker says he's got Conor McGregor's back when it comes to his violent bus attack at Barclays Center ... even though he went a little overboard.
Don't get it twisted -- Travis thinks it's terrible other UFC fighters got caught up in McGregor's window-smashin' madness ... but the blink-182 drummer says Conor HAD TO retaliate after his boy, Artem Lobov, got strong-armed by Khabib's team.
"I would've probably done the same thing if someone punked my friend," Barker told TMZ Sports in Calabasas.