When I've challenged the National Blood Service's ban on gay blood in the past, I've received the same dodgy response each time (on one occasion, it was a skew photocopied note that had been typed on a typewriter - this was 2005). When challenged, their response is that there is evidence that tells them that gay blood is a higher risk group, and therefore they ban all gay blood. The evidence referred to is often from decades ago.
They now proudly state that they've partially lifted the ban to allow gay men to donate blood, as long as they've been celibate for a full 12 months prior to the donation date.
However, that makes no sense. All blood should be tested routinely anyway, and safe sex is much more prevalent in the gay community than it is in the straight community. So, there is no basis for the National Blood Service's ban on gay blood, other than discrimination.
Gay men are excluded if they have sex, even protected sex, with a lifelong partner - even once - in the 12 month period before the donation date. Straight men who have unprotected sex with numerous partners can donate freely.
That's purposely placing an impossible hurdle in the way of gay men, purely to exclude them from donation.
Read this Pink News article about the petition, and then sign this petition to help bring a stop to this nonsensical ban which is discriminatory & adds to the blood shortage ... http://www.gopetition.com/petitions/allow-gay-and-bisexual-men-to-donate-blood-in-britain.html