I am often amazed by how people judge homosexuality is wrong and at the same time being unable to give even one proof, one argument, nothing! And the few argument that a few people manage to put together, don't make sense most of the time. Now of course I am a proud queer I am certainly biased with this. 

But that is not the point, notice how horrible homophobes and ignorants think homosexuality is... Though it's not a big deal, really. Homosexuals don't do anything straight people don't do (seriously!).
Now I am more than ever convinced that the reason is a very basic and rudimentary force that pushes you to anxiously and violently deny others their right for humanity just because they are different somehow, these people usually use the argument of morality, or God or values or whatever. But it was only until recently that I found some form of proof of how unconscious some of our judgements can be.
Read this article with me:  How much thought do we put into our moral judgements?. It is a review of a study about moral judgement and the conclusion is not surprising: 
To take an example provided by psychologist Jonathan Haidt: most people register moral objection when told a story about a brother and sister who slept together, consensually, with no harm arising. Yet asked why they find it objectionable, such people can't explain their reasoning - a phenomenon that Haidt has dubbed moral dumbfounding.
When we make a judgement, we don't really give it much thought, we just judge, thoughtlessly. Most of the time our judgements don't make any sense and they are not based on any rational thinking. You can do the same with homosexuality, just ask the closest non-homosexual person around you about two men sleeping together.... And please let me know what would their answer be.