pick1name is discussing:

An event will be held in London next week where gay and bisexual men will donate blood to be scientifically screened and prove to the government that current restrictions are unfair.

So lets see if I understand correctly. An AIDS infected person may take up to three months to develop sufficient response to their infection to test positive, and so to minimise risk of unwitting transmission by blood transfusion, rules are that no one can donate blood within 3 months of engaging in gay sex, because anal sex is carries the highest risk of transmission.

These activists feel offended that the blood transfusion service is discriminating against them and are going to produce stocks of blood for transfusion which might be infectious despite not producing a positive test, because they are not waiting 3 months, i.e. the test result may be a false-negative.