1. I'm not talking about gay marriage here. 2. do you honestly think there were enough castrated men walking around (probably less than 1% of the male population in 1ce) that it warranted mentioning? beware of Sola Scriptura
A eunuch is not name for a gay person. A eunuch is a man that has been castrated and some men are born that way. I knew a man that was born that way, and I can tell you he never had homosexual feelings.
First of all, a eunuch is someone who has the ability to have sex taken away from them. Many men in a kings high court, for example, were sexually "disabled" so they could not have sex with the kings wives and made eunuchs. Others decided to be that way so they could devote themselves to God, for example, and not be concerned with sexual matters. Therefore, to compare a vasectomy to being a eunuch is absurd. Secondly, we are all sinners. Did God then make us to be sinners? It is both yes and no. Yes God created us, but sin was birthed in the human race via free will and then passed down to succeeding generations. So to cherry pick "sins" and say, "God made me this way so it must be OK", also seems absurd to me. The bottom line is that when the Bible talks about homosexual behavoir directly, it does not cast it in a favorable light. In fact, it mentions it as an abomination. This is done both in the OT and NT. This is what you must come to terms with as a believer, not the bit about eunuchs. No doubt, someone becoming a eunuch to overcome a life of homosexuality could probably be included in the scripture you cited. But then, who wants to be celebate for the kingdom of God? I guess some in the past have, but most want their cake and eat it too.
Just as heterosexuality and homosexuality, pedophilia and zoophilia is also not a choice. As for the cause, I think it may be a mix of genetic, hormonal and environmental causes. Anyway, not a choice.
In ancient Greece the homosexual lifestyle was pervasive due to the culture......or are you going to make some arguement that they were all genetic in origin?