I saw an article where several members of the LGBT community were outraged because they couldn't donate blood in the aftermath of the Orlando shooting. As someone who donates blood regularly I know they ask questions like "as a male, have you had sexual contact with another male in the last 12 months?" If you answer "yes" they do not accept your blood because it could be contaminated without you showing any symptoms yet and they don't want to risk transfusing contaminated blood.