Hang on - you don't get to claim that sexual sin is the cause of unstable families.
A (not the) major cause and it is self-evident. Liberals and progressives have this strange delusion that you can have a sexual climate which both incentivizes and encourages short term and non-committal sexual choices without long term consequences to the population's ability to pair up and create stable and committed family units. It is not that irresponsible sexual choices in isolation bring down a society. But the perverse effects which build up over the course of generations will eventually contribute to the fraying of the social fabric over time.
It isn't the only cause of course. Economic forces and the increasing scarcity of traditional manufacturing jobs have much to play in this as well. But that's a whole different topic.
You're undoubtedly referring to open relationships and potentially things like homosexual parenthood - both of which would be classed as sins but neither can be shown to be at all harmful to the idea of a nuclear family. I have experience of both; a friend who is a wonderful father despite being married to another man, and a couple who have been swinging for decades and raised two kids perfectly fine.
You're overlooking a fundamental truth about human beings. Human motivation is shaped by incentive. I'm saying that a permissive sexual culture incentivizes irresponsible, short term sexual choices and that these choices have detrimental, long term effects
in the social aggregate. You have minority communities in the US reaching illegitimacy rates of nearly 70%. And projections are for the white majority to catch up within decades. If you think that a majority of people not knowing who their fathers are bodes well for a stable society then you're selling basket case of goods. But I don't expect those so invested in the current sexual culture to see the obvious anytime soon.
Secondly, the whole thing about antiniotics is caused by overprescription, not sexual behaviours. Yes, a syphillis superbug might occur - but a chest infection is much more likely due to method of transmission and infection rates. To suggest that its perpetuated at all by sexual behaviour is dishonest (although I'm not saying you're intentionally being so)
I'm sorry, but nigh uneatable STDs are already a thing. Right now it's gonorrhea, but it doesn't take a prophet to see the potential for more serious infections to join the list. And you think that its [said gonorrhea's] spread has nothing to do with sexual behavior? What about the fact that homosexual men represent the majority of HIV infections in the industrialized world? Again, nothing to do with the sexual choices being made by said demographic? I'm sorry but who do you think you're trying to convince? Of course, the potential for something airborne to become resistant is much scarier but the point still remains. We're facing the very real possibility of a future where once treatable STDs become much harder to near impossible to treat. Whether or not such a future puts a dent in the use of Tinder and other such disgusting apps remains to be seen.
In your second parargraph, you make some really bizzare predictions. Of course murdering kids isn't going to be ok (despite your god seemingly being fine with demanding it of his followers). Of course having sex with teenagers will never be ok - although the religious legal "marry your rapist" loophole in some US states tries to make it so.
I'm either paranoid or you're very naive. The fact that recently various states in the US both attempted to and in the case of New York succeeded to legalize abortion right up to the
very point of birth seems to favour my view over yours. And the push to drastically weaken age of consent laws has existed for decades. NAMBLA were a bad look at the time of their height so they were dropped from the gay rights platform, but if you think such proclivities just disappeared and won't be again pushed for as culture becomes ever more permissive then I have one word for you. Twink. I mean, the bulk of the scandal in the Catholic Church was that homosexual clergy were targeting post-pubescent boys for sexual abuse.
The question is this. If consent is the only moral consideration involved in assessing the morality of a sexual encounter, how long will it be until some begin to advance the argument that at least some teens are in fact capable of giving informed consent to older sexual partners? That it shouldn't be assumed that all such sexual encounters are always and necessarily abusive?
How long to you think it will be before some begin to argue that in at least some circumstances, such sexual encounters could be liberating for those teens who are in fact capable of such consent and as such the existence of strict age of consent laws are an irrational artifact of redundant sexual attitudes?
If consent is the only moral consideration, then you'll have no rational leg to stand on in your objections should the law determine that at least some minors are capable of such consent. And if and when it happens I hope you'll remember your assurance that it will
"never be okay". Because I'll have no qualms in saying that I told you so.
The ultimate point is that given the premise of sexual liberation there's only one direction things can go. This drift towards ever more permissiveness and license can be monetarily halted here and there, even reverted in the face of scandal for a time, but so long as the rejection of a teleological purpose for sex is tacitly maintained by the culture at large it will never find an end point. When you reject the idea of a created order and the moral law therein implied, then as it was so wisely said:
"All is permitted". I don't believe humans are fundamentally moral by their unguided nature.
Anyway this is getting long and I'm running out of time. I'll respond to the rest of your reply sometime in the next few days.