My son's father thinks it's my fault that our son is gay?

My son's father walked out on me when he found out I was pregnant and it's only within the past 2 years that he's decided to put in a appearance. He has recently found out our son, Maurice, is gay after he saw him hug his boyfriend. I personally don't think it's a big deal that he likes boys, my "baby daddy" on the other hand is a different story. He believes that since our son didn't grow up with a male figure in the house it has caused him to be gay. He also told me it's partially my fault "for not making him do things normal boys do." He has been attempting to spend more time with him (my guess is that he thinks it will make him "turn" straight) but Maurice wants nothing to do with him. In his own words he would "rather do anything other than spend time with him." Before i drag on any further, what do I do about him? How do I show him that nothing is going to change or son and that he is who he is?