There is multiple fail going on here.
1. The driver of the PT cruiser should know how to change a tire. That's just simple. If they can't do it or expect someone else to do it for them for free, they can just sit in the heat for all I care. And since we're swinging our Good Samaritan E-Peens around, I have stopped to ask people if they need me to call someone for them on multiple occasions. Almost all of them had already called.
2. Whether the officer is supposed to help the person or not, it IS his duty to ascertain if the stopped vehicle poses a threat to moving traffic or not. Same as if it were debris or a fallen load. I can't see any officer saying with a straight face that they aren't responsible for traffic safety. And frankly, short of a rest area, no place on the side of a highway is a safe place.
So the owner of the PT cruiser should not have been trying to get the officer to help with a breakdown. Prepay phones are cheap if they're too lazy to fix the tire themselves. But having failed Basic Vehicle Ownership 101 and asking the officer for help, the officer should have at least radioed it in to get a wrecker out (at the owner's cost). And then indicated to the driver that he had radioed so that the driver can walk off the highway to a safe spot. It wouldn't have taken much of the officer's time at all.
As with most situations, there's enough blame to go around.