While many closeted gays have served with distinction, to open the doors officially would bring a slew of wannabes, leather fetishists, "bears" and affirmative action activists out to prove something politically, but not fit for combat. Imagine the tears and the discrimination lawsuits if a drill sergeant demands equal performance.
And what would be next? -- "Whether the orientation is real or perceived" opens the door to transgenders, including the political test-case applicants. Anyone who spurns advances would be open to charges of bigotry, hate and homophobia. What an expensive mess, just when our economy is tanking and our enemies are just looking for their chance.
I served 12 years in the US Navy and over the years I have met many gay males, all of them are constantly thinking about sex and nothing else. Also before the Clinton administration ordered a change in the way the data was presented in 1997 the FBI crime report for that year showed that in the cases of child abductions under the age of 12 not done by relatives of the child, 98% of those were done by homosexual males. Freud was right in his idea that homosexuality is a mental condition.