I'm going to break a car window when I see dogs left in a car
Do you think the owners will be upset?
I don't care. They should know how terribly hot it is when they lock their dog in a car.
Instead of smashing the window yourself, call the authorities to free the pets. You can be charged with repairs, even though you were doing it for a good purpose.
The dog owners deserve for putting their own safety before the dogs.
I understand you want to help out the pets, but it is not your job to smash windows. Let more qualified people smash the window, you can still be helpful by telling someone else.