I hate my ex wife, if she caught fire I wouldn't p**s on her to put her out, however she is the exception as I am very friendly with a lot of my ex's, including one of my ex girlfriend's who was killed in an accident and whose little boy now lives with us. No reason you shouldn't be friends at all, I mean in theory you once loved this person, that doesn't just disappear overnight even when things go wrong and as long as there as no purposeful hurt then you should still feel friendly and affectionate towards them. I don't think you were being unrealistic.