That is the case in many countryis with blood. The Danish blood bank ran into an issue a few years ago where they warned of a possible blood shortage a few years ago and they then turned down blood from (healthy) male gays.
You can't donate if you had sex with a single male 30 years ago, but I can sleep with all the females I want and still donate.
Those rules came in in the early 80s when we barely had a clue about HIV/AIDS and one of the few things that were clear was that gay men were a higher risk group (though we didn't know why).
Given there are no doubt reliable tests to find and discard blood carrying such things, I'd be interested to know why the rules have not been removed and such tests put in place (it could be that governments don't want a public argument with certain narrow minded loud voiced religious groups, or it could be that the tests are just too time consuming or otherwise expensive).
Religious groups don't have much power here and the rules still exist.
But blood donation rules are fucked. I am banned for life from donating blood in the US -- because I spend more the 3 (or is it 5) years in Europe (I was born here). Apparently every european is considered so likely to have mad cow disease that you are better of not getting our blood at all.
You can't donate if you had sex with a single male 30 years ago, but I can sleep with all the females I want and still donate.