Is it inappropriate to feed my bf french fries in public?

We were in a restaurant/burger house. At some point we were teasing each other and I would feed him fries using a fork. We did it for fun, nothing crazy. And then a client next to us (it was him, his wife I suppose and two kids) asked the waiter to tell us not to do this because his kids were watching.

I felt two things a) a bit ashamed and b) angry. I mean seriously? I ignored him, continued to give him fries and then he came himself and told us that we don't respect his kids. I told him he's the one who's not respecting us because we don't do anything wrong or offensive. Eventually he left furious and threatened the restaurant that he will sue them lmao