Have a gander at this: http://en.wikipedia.org/wiki/Hate_speech_laws_in_the_United_Kingdom
Effectively, the most important part is 'In the circumstances of hatred based on religious belief or on sexual orientation, the relevant act (namely, words, behaviour, written material, or recordings, or programme) must be threatening and not just abusive or insulting.' So, the decision was made on the basis that the pamphlets distributed called for the execution of gays in a way that was threatening, i.e. listing how they should be killed, very loudly and publicly. A judge would be required to make the final decision as to whether something deserved the label of 'hate speech', but that's the case for pretty much any legislation you can think of.
Being jailed for a spoken death threat isn't ridiculous, and isn't anything to do with reveling secrets. Why should it be if that threat was sized up to a whole section of society?