My girl doesn't want me to be a sperm donor and yet I still am.
Do you think it's smart to stay a sperm downer with a girlfriend?
If it makes me happy, then who cares?
Validating your spouse's feelings requires accepting your spouse's feelings without judging them or trying to minimize them. And then it involves responding empathically.
It's not a big deal as I'm supporting her decision.
Her decision was for you to not donate your sperm, so you aren't helping support her decisions. You need to tell her what you are doing and hope that she approves.