I explain to gays that its the same for heterosexuals who are addicted to porn or have a wondering eye. Even though they might be married, if they lusted after another person in their mind, they’ve sinned.
As a good friend and pastor whose brother is living in this destructive lifestyle says, “sexual sin is sexual sin. It can be fornication or homosexual activity, it’s still sexual sin.” First time I’d considered it that way, but he’s right. It’s easy to make unnatural relations somehow “worse sin” than natural but non-married relations. It’s also wrong.