That lady sounds completely nuts. Besides if her Danes are full grown, they can easily just reach those bowls and treats themselves!! If those dogs are offered food, they are suppose to take it that's how it goes. She should not hit them, man if I was there I would have called the cops right then on her! I don't put up with that!

Secondly, you should never give treats to someone elses animal with out asking first. I know the people at petsmart have a tendancy to almost NEVER ask.
I've never told them no, but I will basically say to them, "if your going to give him one, at least give him a command first."
One of my dogs a border jack was going through the NILF style.
Personally I think it's just rude, it's like a stranger turning around and giving a peice of candy to your baby with out asking first, that would totally flip me out.
Plus you never know if that specific animal is highly allergic to something in those treats which are given, you don't want to unintentionally harm the animal.