Given that: Satorum believes homosexuality is horrible and rape of young boys is normal homosexual behavior rathen than abuse and rape:

The only possible logic that makes the above not gibberish is that Santorum isn't terribly concerned when women are raped but he does not like the idea of a boy or man being raped. Since rape of women is not a big deal, man rape absolutely has to go into a different category. He assumes that gay rape is done by gay men, so it's the gay that's the problem. No gay = no gay rape = no rape of men = we can go on more or less ignoring rape, rapists almost never get convicted, a woman who is not chaste cannot be raped, she asked for it, etc.

Not sure if I'm expressing it right but it's making sense in my head.