It’s not really that surprising. I’m straight, and thinking about sex with someone of my own gender, does repulse me. But it’s not really a different revulsion to thinking about sex with someone of the opposite gender, who I’m not into.
I can totally imagine less self aware individuals observing their own feelings, and failing to account for the fact that the feelings of others may differ, and that that is fine, and doesn’t need to affect them. Even if they are otherwise secular.
I’ve definitely met homophobic people, who literally go out of their way to feel queasy about it, when seeing it in public or the media. Mistaking their feelings for something more universal, than just their own personal sexual orientation.