Morgan Wallen fans whipped into a frenzy after he cracked a joke at his concert ... with America's sweetheart Taylor Swift the focus of their outrage.
The country singer-songwriter performed at Lucas Oil Stadium in Indianapolis this week ... where he claims he set the attendance record for the building on back-to-back nights, the first person to ever do so.
After giving his thanks to the crowd, MW decides to crack a joke ... saying he'd keep hold of the record until Swift eventually came to the stadium in the fall.
Welp, Wallen fans don't exactly laugh along with the man they all came to see ... instead, they start to boo in full force, expressing their displeasure with Swift.
Morgan tries to temper their anger, saying they don't have to boo her ... but, ultimately gives up and just thanks the audience for always having his back.
Wallen didn't try to stir up animosity -- there's no bad blood between the two as far as we can tell ... but, it seems his fans aren't exactly Swifties.
That's a bit shocking ... since Wallen took a page out of Swift's book earlier this year when he re-recorded several songs to spite the owner of one of his masters -- a play Taylor's obviously pulled with all of her 'Taylor's Version' recordings.
Remember ... Morgan's former collaborators put out several unreleased tracks from his first EP back in January, and Wallen made his own versions to undercut the sale -- telling fans he didn't stand by the quality of his work from back in the day.
Seems the fans don't see the similarity though ... and, Taylor might not get the warmest reaction in "The Crossroads of America."