system
Given the following post, respond as if you're commenting on Reddit:
human
CMV: Men who have sex with men (MSM) should be allowed to donate blood, without a "waiting period" which can range from 1-5 or more years. Lifetime bans are discriminatory.

Blood banks in many countries are continually trying to get more people to donate blood due to high demand and lack of supply. Yes, gays are a small fraction of the population, but, as they say, every drop counts. Additionally, blanket bans and "abstinence periods" are discriminatory. 

The safety of the blood supply is, naturally, of paramount importance. For this reason, there are many tests run on collected blood, and there are many questions one must answer (truthfully) when attempting to donate blood.  

One such question is (in my country): "Have you had sex with a man or a MSM within the past five years". 

I will allow that the gay population does have a higher incidence of HIV/AIDS. There are several reasons for this which we can debate if you wish, but this is, I believe, a diversion from the topic at hand.

I contend that a better question to ask would be "Have you had unprotected vaginal or anal sex in the past year". 

Additionally, another requirement which I would support would be a recent (~ 3 months, for example) STI panel.

If those requirements are met, then I believe a gay man who has only protected sex and has regular blood tests should be allowed to donate blood: in the same manner as a woman or man who are straight. 

The essential issue boils down to the fact that MSM are treated differently even though they, like myself, practice safe sex and get tested regularly. 

In my own country of Canada,  I cannot donate blood because I've had safe, protected sex with other males, despite the fact that I have never had an STI, and get routine checks. 

In order for me to donate blood, I don't need to have protected sex and be conscientious; I have to abstain from (protected) sex (with males). Then, my blood is safe enough to use.

CMV.
gpt
I think you answered this one yourself:

> The safety of the blood supply is, naturally, of paramount importance. 

This isn't an issue of the rights of gay men or Men who have sex with men to give blood. This is about the rights of people who receive blood transfusions (Often with no say in the matter as they'll be in a bad way at the time by definition) NOT to receive potentially contaminated blood.

And furthermore because of the way blood is banked and distributed, it's not on a case by case basis. Blood borne viruses could destroy a large amount of otherwise viable blood.

The sad fact is that certain sex practice leave you more open to HIV/AIDS and the medical service has done the maths and worked out that the small gain in additional donors is absolutely NOT worth the risk to blood supplies and patients of contaminated blood.

Same as intravenous drug users, you simply have to accept that some lifestyles are high risk in certain respects, and that may preclude you from giving blood. It's not discriminatory, it's protectionist.