By that definition hetero sex which isn't done strictly for purposes of reproduction is every bit as "perverted." If you've ever had sex with a woman, for purposes of pleasure alone and with no intention of inducing conception, then you're a pervert. That would include even with your wife. You've said here that taking pleasure in it is OK if that is a secondary benefit of the act, but the "primary" purpose must be reproduction. That would rule out, for example, having sex with your wife when you know she isn't ovulating, because that would be for pleasure alone.
If that is their view of sex for pleasure, then they need to be consistent. A kiss alone is not necessarily sexual in nature, but if the theory is that a kiss can be sexually pleasurable in and of itself, and I agree it can be, then they need to condemn it wherever they see it in public, because obviously a kiss in public is extremely unlikely to lead to reproductive intercourse.
These people are condemning this because they don't like gays and lesbians. They don't have any justification for this . In this case, there isn't even a biblical prohibition because the Bible says nothing about relations between women. So who are they to decide for everyone else that sex for pleasure alone is bad, much less to apply the principle selectively to only one class of people who are doing it? For crying out loud, women are only fertile at most 7 days out of every month, and not at all after menopause. The vast majority of hetero sex which occurs in this world is done for pleasure and pleasure alone, where the participants know there is no chance of conception.
You're torturing logic and reality to justify the bigotry of others. Disgusting.