That's right. The whole "He is under no obligation to [do nice thing | be social | act friendly]" is a very Reddit attitude. Yes, it's technically correct: You don't have to be nice. But you are allowed to be nice, and that choice doesn't hurt or cost anything.
If you go up to a fellow parent and say, "Hey, nice to see you again." and they just ignore you scrolling their phones, sure, they have a Constitutional right to do that and are under no obligation to return the greeting. But going through life only doing what you are "obligated" to do seems like a very miserable and anti-social way to live.
If you go up to a fellow parent and say, "Hey, nice to see you again." and they just ignore you scrolling their phones, sure, they have a Constitutional right to do that and are under no obligation to return the greeting. But going through life only doing what you are "obligated" to do seems like a very miserable and anti-social way to live.