Soon to be baby father giving me an ultimatum 🤧

So my son is 8 years old and I breastfed him until he was 2. I’m currently 5 months pregnant. My son seems curious to taste my breast milk after the baby is born. He always asks why I never continued pumping and gave him cows milk instead of my milk. I know my son is going to ask to taste my milk. I don’t plan on giving my son cups of my milk, just for him to taste if he asks. Children get curious. I’m not going to tell him no to tasting it.

My soon to be baby father who is not my sons father is upset that I will be letting my son taste my breast milk. He said it’s “incest”, he said bcuz my son is not his son that my son shouldn’t be drinking my breast milk. He says that it’s his baby’s breast milk and his breast milk.

So then he proceeds to tell me that I don’t listen to his wishes and if I don’t agree to not let my son taste my breast milk then we can’t work out a relationship. I don’t think that should be a reason for why him and I can’t be in a relationship.

What are your opinions on this situation? Should I let my son taste my breast milk? Should I listen to the soon to be baby father ? Do I focus on my son and ignore a relationship with the guy?