Upvoted, even though you're wrong.

You seem to be saying, in essence: allowing gays to donate doubles the number of instances of transfusing HIV while only increasing the number of lives saved by 7-10% (or 20%, or 2% - it doesn't matter). But that's the wrong way to look at it. Even if 10% of all transfusions from gays resulted in an additional HIV infection (thanks to testing etc., I'd guess it'd be well below 1%), that still means that, for any given transfusion candidate, you have a 90% possibility of saving their life without transfusing HIV.