All anal sex in the US requires a 3 month waiting period (as does any kind of sex with a new partner) not just male to male.

Anal sex is inherently much more likely to transit HIV and HIV tests have a higher false negative rate for new infections.

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.

0.4% of the US population has HIV.

12-15% of gay men in the US have HIV.

The rules exist for a very real reason.