My opinion is - and I am going to go with completely rational, evolutionary standpoint: people (and more likely men) do have affiliation to see their offspring to the next generation. Meaning it is in our primal nature to further our genes, that is why we have children. His reasons for donating his sperm are his own. He doesn't owe you an explanation nor the reasoning to do it - he isnt doing anything wrong, forbidden and illegal.
I fail to see your logic here " It makes me really uncomfortable to know that there will be his offspring running around"....Uhm, what? You will NEVER be in contact with hi offspring, and why would him having offspring tick you off so? Because you don't have children? is this maternal jealousy I feel here. The same type step mothers feel for their step children.
You are aware he isn't actively participating in sexual act when he is donating, right? And also he will have no contact whatsoever with his future children (if he even has any, note that not all sperm gets picked).
And in the end of the day if it bothers you so, the doors are open for you to leave. Having issues with his own personal choices will come to bite you in the end later on when (or if) you are married.
The reality is that with DNA testing and registry's like Ancestry.com - the children born of a sperm donation may well have access to their blood relatives and that may or may not be a good thing for some. Say a husband donates sperm, 20 years down the road is divorced and maybe on the outs with his ex and maybe this has affected his relationships with his "actual children". I would feel a connection with any child of mine, given up for adoption or egg donation, if all was said and done and i met them through a DNA site, i might feel a sense of moral obligation to provide for them if their lives took a hard turn, and that would certainly affect my own children's legacy. DNA testing is a game changer.
Is there a place where you live where plasma is donated? You can make money doing that too and it does save lives. My dad needed quite a few units when he got sick. Something to think about.
I can see why this would bother someone. Most likely he'd be protected and the future offspring from his sperm would not ever have access to who he really is. Sperm banks are pretty good about that. It's different than adoption where a child goes back years later to find out who their real mother and father are. But there is always that . . . what if feeling.
There has to be a better way for him to make money. :>) Talk about what else he can do if it bothers you. You are entitled to your feelings and hopefully he is open to hearing them. He may overrule you and do it anyway but at least he knows where you are coming from.
Let us know how it turns out.
I just read your posts from last spring, where you talked about the anxiety you had in your relationship with your boyfriend. You had broken up for about three weeks and he had had sex with someone else, and you had snooped on his Snapchat, he had tried to hide it, you just could NOT get over that he had sex with someone else when you were broken up. You were talking then about moving in together in July. Is this the same guy? Is this just a continuation of the same argument in a different way?
First of all, he is your boyfriend, not your husband and not your minor child. You don't have the right to stop him, any more than you would to prevent him from donating blood. I realize you probably understand this and are coming at it from a "this will bother me" angle and not a "I have veto power over this" angle. But maybe it will help you if you remember that it really is his decision and his alone.
Second, a sperm donor is not a father. He merely produces sperm. It is likely he will never even hear what the results are. If children are born of his donation and a woman's egg, he will still only be the donor of half of the child's genetic material, someone else will be the father, not him.
Is part of your problem that you are afraid someone will come at him later in life and want him to be sort of a quasi family member? It's not likely to happen. (I've been at one meeting of two kids who were genetic half siblings and their donor, set up by one of the kids' parents, and guess what, they were not interested in each other. Possibly the donor was slightly interested just to see what the results were. It didn't result in any more meetings.)
Are you worried that you will want to know what happened, and who the woman is, and what the resulting baby looks like, and all of that? Oh dear. It's not like his sperm is a proxy for him and is out getting a girlfriend, or anything. Would you feel that way if he gave a plasma donation and it saved someone's life? Or would you just say "That's nice," and think no more of it?
Maybe it would help to think through why you would call a child from his sperm donation and a woman's egg "his offspring." It is not like it might be if he had a bunch of actual kids to whom he had 100% legal right (such as, he's a single father and their mom is dead) and he cavalierly threw them out into the world as babies with no care for their future. It is no simple thing (emotionally or medically or, probably, financially) to use a sperm bank to have a child. Parents who have gone that route are some of the most motivated and caring parents in the world, because it's often their last hope after many tries. The kids born from that kind of arrangement are those parents offspring, not the donor's offspring. Sorry.
If you can't live with it, you can't live with it, and if so you should let your boyfriend know. But I do think he has the right to do it and that you are making more of a big deal of it than you should.