The negativity extends even to the menstrual cycle, and seems particularly focussed on women. Surely we have moved on to have a far better understanding of sexuality than this negative harmful view of human sexual behaviour.
You know, I don't really think this is true. There is a weird obsession with emissions of all sorts in the Old Testament, not just about menstruation. Ritual cleanliness in Judaism is significantly bigger than just sexuality--look at things like leprosy and touching corpses--so reducing it to negativity towards human sexuality seems like a bit of a stretch. I'm not sure why ritual purification is such a big deal in Judaism, but whatever is going on, it has implications for sexuality rather than being specifically about sexuality.
A couple thoughts on the rest of your comment:
Instances of concubinage or polygamy in the Bible aren't necessarily portrayed in a positive light. I find the story of Jacob, Rachel, and Leah striking because of how
negatively it portrays polygamy--it led to nothing besides competition and dysfunction in that family, which culminated in Joseph being sold into slavery. It's dangerous to take just about anything in the Old Testament at face value, though, because one of the major themes is human
frailty rather than righteousness.
Not everyone who is in favor of traditional sexual ethics is so because they think sex is "dirty" (though many clearly do fall into that category). It's a bit too conservative for me, but I'm somewhat sympathetic to the theology of the body of Pope John Paul II, for example, for whom sexuality is sacramental in nature and ought to be treated with utmost care because it is holy rather than because it is dirty.
It also needs to be taken into account that sexuality can and often does become sinful and harmful, given how easy it is to slip into objectification and entitlement. I think negative views of sexuality only contribute to this problem, but an elevated view of sexuality does involve putting a proper emphasis on abstinence as well. Lose that, and you end up with 4chan psychopaths who think they have a "right" to women's bodies.