IMHO it depends
I used to leave my dog in the van but i lived in a van so had little choice and it had open vents and it was insulated. Occasionally she would go and sit up front to have a look for us coming home
I ended up with a sign in the window explaining all this as i got some abusive messages and one confrontation.
If it was really hot I would tie her up to a wheel with a rope and she would sit under the van . It was a classy look 😉
If they made no attempt to park in the shade on a bright summers day then i think I would say something everything else is one of those.