You are on to something here. I have always said the same thing.
If sodomy is okay between a man and a woman, what would be wrong with it between two men?
When Sex is thought of as less than a sanctified union between two married people, and more of a recreational activity between two consenting adults; then there is no argument against homosexuality!
The term "sodomy" can be applied to many different acts. I would suspect that for many people, the specific act is probably more important than the sex of the participants. I would expect that if one were to ask people to rate different acts on a scale of 'icky' to 'just fine', that mutual masturbation by two men or two women would probably be, on average, judged less icky than anal sex between a man and a woman. So the fact that people view anal sex by two men as more 'icky' than oral sex my a man and woman would not necessarily imply an anti-gay bias.
In practical terms, though, it should be noted that there's a difference between gay anal sex and hetero: of all the sexually-transmitted-disease vectors, anal sex by an infected male is the most effective; it is far more effective than any vector by a female. Consequently, if an infected male performs anal sex upon another male and transmits the disease, the recipient is more likely to retransmit the disease than would be a female who received it.
BTW, I have sometimes commented that liberalism includes a belief that it's more noble to curse the darkness than to change a light bulb. I don't like to ascribe motives to people, but given that AIDS risks are well-known, I sometimes wonder if people somehow think it's 'noble' to contract AIDS to help expose how the evil Republicans are responsible for its spread. There is some very bizarre social pathology at work, which I haven't really seen addressed, which is much scarier than the virus itself.