People knitpicking your car.

I let 'em nitpik. Sometimes someone comes up with something I want to change and they have a decent (interesting, possible, cost-effective) idea.

If someone wants to be obnoxious on the correctness, I just say. "The goal was not a concours quality restoration, just a driver I could enjoy. I've done a concours restoration, not many fully appreciated what went into it. Have you ever tried to do one?"

At that point, they usually either leave or enter into a more polite conversation.