divorced parents vent!!!!

My parents divorced just over 10 years ago. Things didn't end well my mother left my father for another man and he never got over it. I was always closer to my dad and struggled with my mum but in the last few years my mum and I have become a lot closer! Yay! Anyway I'm about to have the first grandchild and my dad is being funny about my mum! My mum has been great through my pregnancy and phones me everyday! Well today I put something on Facebook about Nannie wanting baby here and I get a shitty text off my dad calling mum mum granny grotbag! I'm so frustrated! This is my first child and I want to enjoy it not have to deal with childish arguments on my dads part! I get he was hurt and he'll never like my mum but for gods sake I'm not going to choose between you! She's my mum and will be in mine and babies life as will my dad! Sorry just need a vent especially seen as baby due in a few days!!