Sinning, as Jesus and the church say, is good. Turn or burn Christians.

[The Grand Nudger]

??

There are no evil or sinful sexual fantasies if it is consentually based.

I cannot speak for the other type.

The urge to mate would be sin, not sex of any particular kind.   The thing that compels, not the thing you do on account of it.  All things derived from that urge would be sinful things, all evil.  Consent, no consent, samesies.

As to your understanding, not surprising. We were more in competition for the supremacy of ideas that cooperating.

Which begs the q...who am I trying to fuck?  If the urge to mate is sin as you describe, and this is what engenders conflict in human beings, which is our barometer for evil....who's the lucky girl?

As a Gnostic Christian, I find it fairly easy to see and use analogues terms between the various ideologies and theologies. Sin, crime, evil, bad, --- while each has it's specific definition, when I balance things out, they are all on the same side.

Perhaps, and I hope, that that penchant is what made the older Gnostic sects more moral than Christians as it allowed us to see Yahweh for the prick he is.

Regards
DL

That's the general notion, yeah, that all of these things are related.  Sin is the thing that compels us to evil, bad is a descriptor for those things, and crime is a subset for which we have laws.  Seeing as how all of these concepts are immensely consequential in our lives, we should probably have an accurate understanding of them, and I don't think that fingering the urge to mate as sin is that description.  

In the wider view, sin as intrinsic to human beings, you couldn't be more moral™ on that count.  You have a different religion, but you still have the urge to mate which still drives you to competition.