Some stores I have been to have the magazines in plastic bags with a sign that says DO NOT OPEN MAGAZINE bags, so if there is a major problem at this location, they should adopt such a plan/ policy.

I think that it is totally fair to look through a magazine to see if it interests you before you purchase it... It would take a long time to read the whole thing, and if you are just checking out an article without damaging it, then it should be OK.

And kudos to you for speaking up and calling him out on being rude. I would choose a different location in the future, or a different store altogether.