MSM is one of the highest risk activities you can do for bloodborne diseases. If this is discriminatory, life is discriminatory. Life is not fair, and there is nothing any artificially constructed social system will ever do to force mother nature's hands to make life fair. I fully support the rights of people to love and be in relationships with whoever they wish, but that doesn't mean you have the right to contaminate the blood supply due to the inherently high risk of your day-to-day life.
I have never been able to donate blood because of my travels due to their locations and frequencies. I am not going to give up travel to donate blood. MSM is a much higher risk activity than travel, and yet I am also excluded due to my lifestyle risk. It's not fair, but it is reasonable.