Dave Portnoy is a big fan of Dave Grohl ... but he can't wrap his head around why the Foo Fighters frontman would pick a fight with Taylor Swift -- telling TMZ Sports he believes the pop superstar is the real deal on the stage.
The Barstool Sports founder -- who is very vocal about his love for T-Swift -- weighed in on the music industry's newest beef this week ... and he said going after the Swifties' "mother" is a fuse you don't want to light in the first place, but especially when it's over her performance skills.
In case you missed it, the Foos were having a concert across the pond in London over the weekend -- right in the middle of Taylor's takeover in the same city. While onstage, Grohl referenced the "Eras" tour, then said errors are bound to happen when musicians actually play live music -- implying the pop star's shows are mainly supported by recordings.
While fans at Grohl's show applauded his statement, Swifties certainly developed some bad blood with Grohl. Pres knows those supporters aren't the ones to mess with ... explaining they won't play nice when defending Taylor.
"If the Swifties come for his throat, burn down his house, that's what happens when you come for the Swifties during the middle of a concert," Portnoy said, shrugging his shoulders.
Pres would know -- he attended Swift's tour back in May 2023, so he saw her crush the stage with his own two eyes.
Portnoy -- who also talked to us earlier this week about his second One Bite Pizza Festival -- wanted to make it clear, though ... he likes Grohl and the Foo Fighters -- but the rocker's comments might not be worth it in the end.
"I don't know why you take that shot," Portnoy said. "Don't cry to me if they come after you."