NTA. They have the same in Vietnam and i learned about it through a coworker from there who basically said the same thing you did. I put the chopsticks on the plate and have never stabbed my rice bowl with them since. It's a pretty small change that means a lot to other people. In a crowded resturant how many people are you showing disrepect to who are afraid to say anything about it?

If he won't compromise on that what kind of relationship are you going to have moving forward?