Again, this is one of those instances where, personal feelings aside, what matters the most is the science. Do the numbers show that it's safe to use blood from gay men? How do those numbers compare to straight men? Women? The ultimate goal is to have a blood product that is as safe as you can possibly make it.
I agree that science matters more than personal feelings. Indeed I had quite a clinical view of the issue as long as I only dated women. From my perspective, it was about keeping the blood supply safe, and the historic reasons for the MSM ban were well-known and (as you say, Lali) justified at the time.
What caused me to change my perspective on the issue was the prospect of, ironically, (protected) heterosexual intimacy with someone who had had a single (protected) MSM contact. I can scarcely put into words how that made me feel, the idea that monogamous, protected intimacy between two people who had been very safe and restrained in their intimate practices -- and who had tested negative for all STDs more than six months after their last sexual contact -- should
make my blood unsafe to donate, in my government's view (a woman who has sexual contact with a MSM is subject to a one-year ban after the last contact; if you are in an on-going relationship with such a MSM, you are ineligible to donate). At an emotional level, it felt like an assault, an indictment - almost like, "You choose to be with someone who is 'dirty', so now you're 'dirty' too." (even though, ironically, we were both 'clean') The rule became even more outrageous, in my estimate, because I could choose to have unprotected heterosexual contact every night of the week with men who had only been with other women, and I would remain eligible to donate -- even though that would put me at extremely high risk for any number of STDs, including HIV. In view of this fact, this hypocrisy, it became impossible for me to view these two anti-gay bans as remotely connected to safety. There's something so viscerally painful about the government judging your very blood unsuitable for donation
based on your engaging in responsible, safe, protected sexual practices that are objectively far lower-risk than the sexual practices of people who remain eligible. I did not understand this when I identified as lesbian. I also do not think that bans based on overseas residency or tattoos are comparable, because these things are not loaded with the same kinds of moral judgments and practical discrimination.