Pet Peeve

I'm trying to teach T manners... to say hello, goodbye, please and thank you.  T says hi to everyone he sees and bye to anyone he sees leaving through a door.   It's annoying when my child is standing right in front of an adult and he says "hi" and this adult ignores him.  Would it kill you to acknowledge his presence and just say hi back!?  It is just RUDE!  I don't care that he's just a child.. he's a person and he is greeting you-- don't ignore him.  

End of rant.