I hate the term 'baby daddy', it sounds trashy and just yuck.   To me it sounds like you just slept with some random guy and got a baby out of it, like you don't know the guy at all.  Or like you belong on the Maury Povich show!  Sperm donor is pretty gross too, have some tact, it's not like you didn't consentually have sex with this person, if you made a bad choice, live up to it, don't make yourself sound like trash. 

I still laugh because I remember when I came home from living abroad and my sister was singing that song "He's just my Baby Daddy" and I thought she made that sh*t up......

How else are you suppose to refer to him? I mean its the obvious he is the baby's daddy or some may say "My Child's Father"......... sucks but hey it is what it is.

Also one of my pet peeves! I refuse to use that term and just refer to my 'daughter's dad' as just that.