As a gay man who would like to donate blood I fully support this move in the UK. The most important thing to remember is this will make the blood supply safer. MSM will be much less likely to lie about their sexual history and be honest. If one focuses on sexual behavior rather than classes of people, one can also target heterosexuals who partake in high risk activities, thus further lowering the risk.

The one year window is necessary since the test looks for antibodies. If one just got infected, the test would miss it, since it takes a while to develop antibodies. Therefore the one year windows ensures that no one slips through who is in fact infected with HIV.