I'd do nothing.
Several times I have honked my horn on the freeway to get peoples' attention to tell them they have flat tires or other things wrong with their vehicles. Every time they have flipped me off or ignored me. Once I was sitting behind and to the left of a small car in a traffic jam when flames started shooting out from the bottom of the car, like a fuel line fire. I GOT OUT OF MY CAR, and ran up and tapped on his window, and yelled "Your car is on fire!!" He yelled back, "F*** You!" I got back in my car, and about a minute later his car was filled with smoke, he pulled over to the shoulder and got out and danced around as it was engulfed, as I slowly drove past it, so I honked and yelled, "HEY...F*** YOU!"
I was on the Connie a few years ago coming down from Snoqualmie Pass here in Washington, and I caught up to a pickup truck pulling a big flatbed trailer with some equipment on it. He had a lot of smoke coming from his right rear tire, and he did not see it. I pulled up even to his drivers' door, and yelled and pointed, trying to let him know he had a brake fire going on, and he gave me the finger and accelerated away, downhill. A couple of miles down the road, there he was pulled over on the shoulder with a flaming tire.
I few years ago I called a home owner who has a summer cabin across the road from me, but lives in the city, to let him know he had a broken fan on his cabin's heat pump and it was rapidly destroying itself. I was told to mind my own business, that I had no business "Messing with his property", and he hung up on me. The heat pump lasted another few hours until it seized up and quit.
I'm sort of sorry to have this attitude, but too many times I've tried to help people or tell them that something was wrong and gotten crap for it. I'd figure he didn't trash that tire during the present ride, he probably left home with it that way, so he willingly took the risk.