The A-lister was on the ground these past few days down in Austin -- where the U.S. Grand Prix's been taking place all weekend -- but on Sunday ... the guy skirted out of an interview with Sky Sports' Martin Brundle ... a famed former race car driver turned pundit/journalist.

Brundle -- who's well-known these days for his grid walks, where he interviews celebs (sometimes awkwardly) impromptu -- got a bit of a cold shoulder from BP in person.

Now, in Brad's defense ... he didn't totally not respond to Brundle's questions -- ones about the movie, which he says can't answer since it's top secret -- but clearly didn't wanna chat. It would seem like a no harm, no foul sitch ... but some online are offended on MB's behalf.

Brundle himself seemed perturbed -- saying to the camera, "They're known at 'pit stops'" if they don't want you talking to Brad Pitt. Bird app users are mostly agreeing, arguing he should respect the culture and talk to Brundle, whose interviews are par for the course on the grid and who's an F1 staple. In other words, play ball when you're on our turf, Brad!

It's not the first time a celeb has brushed off Brundle -- Megan Thee Stallion famously did it last year -- but in this case, some are suggesting that since Brad is literally making a film about F1 ... he should be aware of the major players, Brundle included, and show reverence.

Outside of this salty interaction ... Brad has mostly been receiving the rock star treatment during his time in Texas, at one point posing for a pic with the Williams Racing team. He's still a golden boy in Hollywood -- and this won't change that.