Rob, My first wife's husband is like that - he never says hello - and also has this stranger kind of distance about him. I used to take it personally - until I just allowed myself to accept it as his own hangup - and just one of the signs of his insecurity (I later learned from my S12 that her family still talks me up a lot...and I doubt that goes over well with him).
So, yes, it's rude and disrespectful - but you can always stay above that way of being - since, in the end, his issues are about himself - and so long as he never does anything to interfere with your rel with your D - than I would suggest you stay clear.
And...I just have to second what Kalni said...if your X continues to be like my STBX than cordial just never works - it just seems to be something she/they(?) can use to get what they want...
When my first W's X says nothing to me - I still just say hello to him - and allow him to be a lesser man. It is his choice, after all.
