I don’t think that being rude (yes, I call it rude when you purposely don’t greet someone) is what the Torah wants from us.
Therein lies the problem. People determining right and wrong from their “feelings” about what the Torah demands from us. What does a Talmid Chochom tell you that the Torah wants regarding this question. Not your “feelings” which are certainly derived in large part from the non Torah world, about what the Torah wants from us.