I know some of our conservative friends would object to the charge that they actually "hate" gay people, but I think the overwhelming evidence from the anti-gay protests--whether in the form of wingnut blog postings, cable television shout fests, or "pro-family" interest group press releases--says about all we need to know.
So, why do conservatives hate gays? I'll give it a shot by suggesting several alternatives, then try to explain the basis for each.
a) The Bible condemns homosexuality, conservatives believe and follow every apparent command in the Bible, so by deduction, gays and homosexual behavior are to be hated and opposed so that God may glorify the nation;
b) Gayness undermines and threatens family unions and society's procreative future and consequently, leads to the downfall of the nation and civilization;
c) Gays are "different", and gay behavior is just "offensive", a deviance, a perversion that tempts our children to unproductiveness and places our culture at risk.
a) probably deserves more elaboration than I will choose to give it here, but I think it is fair to say in brief that few people if any believe or follow every example laid down in scripture. The Bible doesn't explicitly condemn polygamy, for example, and even appears to command it in some circumstances, such as when a brother has died without producing male offspring and the surviving widow is to be taken by a surviving brother of the deceased man (seemingly regardless of whether he is already married) to wife in order to provide the deceased man a family line (Deuteronomy 25). Yet polygamous relationships are something society seems to have decided are undesirable. Slavery gets a pass in the Bible, too (Exodus 21). Yet modern society, for all its decrepitness, has come to the conclusion that slavery is distasteful and immoral, even if the basis for that conclusion was helped in part by slavery's declining lack of usefulness economically. Furthermore, the Bible appears to condemn the eating of shellfish, pig meat, and prescribes a host of other health related guidelines that I suspect most people affiliated with Focus on the Family have conveniently discarded. In the Bible, people were stoned for breaking the Sabbath, killed for fornicating with neighboring tribes, for erecting "idolitrous" images, and so on. Finally, the number of references in the Bible to homosexuality are few, and in some of those, the actual behavior being condemned could be, and is disputed.
But perhaps even more relevant is that while some opponents of gayness reference the Bible in the course of their objections, it doesn't sound as if it is for God's glory they are reacting as they are. Rather, their concern seems to lie elsewhere. Such as in--
b) Gayness as threat to families and civilization has emerged as perhaps the most commonly cited concern by opponents. There are a number of unstated assumptions and premises underlying this origin of gay-hate. One is that although believed by conservatives to comprise less than 10% of a society's population, gayness, like a disease, is capable of spreading, influencing individuals who would otherwise hook up with other-sex partners to "choose" same sex partners instead. The result of such choices is that the desire to hook up with other sex partners declines, the desire to marry and produce families declines, and there is a groundswell towards homosexuality soon rendering a society extinct as it fails to produce offspring. National decline is a big crisis word conservatives serve up in the context of the gay debate. As acceptance of gayness grows, community heterosexuality grows weaker, heterosexual marriage becomes "under seige" by newly loud and vocal opponents of marriage, and, well, you get the idea.
All of this sounds rather implausible to me. Sometime last spring or summer when the gay debate was heating up I emailed Glenn Beck, one of the many right wing radio hosts out there with his own book and asked him how if homosexuality was much rarer than the numbers he claimed are cited by gay activists, then what exactly was the threat from homosexuality? He didn't respond to my email. Imagine that. Maybe there's more to this point, but I don't see it, and highly doubt whether conservatives themselves take it very seriously either, which leads me to--
c) Gayness is just deviant, corruptive behavior that offends some people. This sounds a lot like b) above but without the necessity for demonstrating the catastrophic consequences from homosexuality. It argues, instead, that gayness is just bad, not normal. It's reasoning is circular. Gayness is a threat to families and marriage because gayness is a threat to families and marriage. How exactly? If gayness is rather limited in the population, how does it threaten the inclination for heterosexual marriages and reproduction? Does it make marriage seem somehow "dirty" or not special to heterosexuals? If this is the case, that gayness is such a threat to families, than families must be pretty fragile entitities. This is the underlying cry from opponents of gays and gay rights. Families are "at risk", "under attack", etc. Families must be pretty weak, which makes me wonder if they are, why should we be propping them up? If families are so vulnerable, then maybe there are bigger problems out there than gays.