2:42 PM PT -- MGK just got on Instagram to address the vandalism, letting whoever did it know they got the "wrong" bus, and making fun of them for staying up til nearly 5 AM to carry out the crime.
Machine Gun Kelly is not getting a warm welcome on his tour stop in Nebraska ... one of his buses was just tagged with graffiti, including a homophobic slur.
As you can see, someone spray-painted both sides of MGK's red tour bus ... with one side reading, "RAP DEVIL F*****." The other has an image of a penis ejaculating along the side of the bus.
MGK is playing a show Thursday at CHI Health Center in Omaha ... and folks who are there say the bus was tagged while it was parked on a curb downtown.
The rapper's brought at least 4 tour buses to Omaha ... one yellow, one red, one blue and one green ... but it appears only the red bus was tagged.
It's the latest incident on MGK's cross-country tour, where his opener is Willow Smith ... as we reported, a fan fainted in the crowd during Willow's set on Tuesday in Pittsburgh, but she stopped the show until the fan was moved to safety.
Originally Published -- 11:17 AM PT