In America maybe? I don't live in a violent society, you can spend decades not getting involved in violence but every spring there is sex in the air.

I live in Britain actually.

The Church is definitely saying sex is bad, sex is a sin, must only be used for making children, not for pleasure, even in married couples.

It's insane.

If you mean the Catholic Church, that is incorrect. That teaching is that sex is good, sex is not a sin by itself, but must happen in the correct context of a mutually consenting married couple and must be ‘open to conception’ (i.e. no artificial changes to the procreative ‘mechanisms’, such as condoms or birth control.) They even teach ‘Natural Family Planning’, which is basically how to enjoy sex in rhythm with woman’s fertility cycle so as to ‘naturally’ avoid conception.

Not practicing Catholic anymore but that’s what I was taught from the Catechism et al several years ago as a convert.

Sex clearly isn't a sin unto itself because it's needed for making children, so it's not that. If this was it why wouldn't pornography of married couples be a-ok?

You missed the "not for pleasure" part.

No I didn't, by your logic breeding pornography of married couples should be ok.

Come on, that's ignorant. Nobody is saying that.

I went to a Catholic secondary school. Some people definitely were saying that.

I did, too, and never heard it. Maybe you're confusing the idea that you shouldn't have sex not for procreation (ie the stance against birth control) with the idea that sex is only for procreation? IOW the Catholic teaching is that procreation is a necessary but not sufficient reason for sex.

Plausible. It was about 20 years ago now.