Let me preface this by saying that I don't think there is anything inherently wrong with waiting until marriage. That said, pretty much everything you said here is total bullshit and can't be generalized to everyone.
The claim that there is no such thing as no strings attached sex is flat out ridiculous. Plenty of people, myself included, have had sex with people that they had no emotional attachment with before, and no emotional attachment with later. Sex isn't some magic feelings generator - it can definitely bring people closer together, but that doesn't mean plenty of us can't enjoy sex without become "chemical slaves" to one another. Saying that abused partners stick around because they are addicted to "hormones" is pretty fucked up too, for the record.
I believe that some people "give a part of themselves away", but once again you can't generalize this to everyone. Plenty of people are able to leave the past as the past and be happy in a relationship.
It does not become less special, and if it did once you started sleeping with your wife regularly it would become less special anyways. Sex is less like an object and more like say, food. Sure it might not always be amazing, but it's always satisfying and the potential is there for it to be fantastic, even though you have experienced it many times before.
STD is black and white, either they did or they didn't. Statistics on this kind of stuff don't apply on an individual level.
Flipside: how are you going to feel when you get married and are sexually incompatible? I would rather risk a bit of short term pain (spoiler: getting dumped when you aren't sleeping together still hurts) than risk a lifetime with a dead bedroom or divorce.
Totally agree with your last point about knowing your partner, but if you don't think you can learn new things from new people you're kidding yourself.
Overall I don't disagree with your choice and honestly am impressed by anyone that holds out, I just feel like the way you present your argument is incredibly naive and really just highlights a lack of sexual experience (which I guess is par for the course). I guess it just sucks to see people justifying a decision with shitty logic when the decision isn't one that requires any justification.