Being a child that grew up with a single mom back in the 70s, Fathers Day to me was always a very uncomfortable time. At school, we would make Fathers Day cards for our dads, and I usually mailed one to my dad, and he hardly ever responded.
Being a parent is not just about how you treat your child; it's also about how you treat the other parent. If you treat that person with respect, that's fine, that's the way to go. But if you don't, you're not being the parent you could be.