I think when people are obsessed with the private lives of others, and deny them rights because they do something that they personally find a little 'icky' (but is harming no one) is where nations come undone, and doom themselves.
A private life is a private life - it is when one gets involved in someone else's private life that things turn to custard.
It is when a nation becomes obsessed with other's consenting private lifes, that they neglect to look around them at the other things that are going on - that should concern them more.
Focusing on sexual matters allows more dire concerns, such as terrorism, poverty, health, to be pushed aside, ignored, or contentious laws get passed through quietly whilst everyone is focused on something that REALLY shouldn't concern them.
So is it sexual matters causing the dooming? No. It's the focus on it - something that really shouldn't be of such a huge focus - that detracts from the REAL picture...the things going on in the background that no one is noticing.
We see it here in New Zealand - Contentious and divisive issues for the government are given a lot of media coverage, and laws that are likely to not have gone through if the public had been aware are passed. Such as the Anti-Smacking Bill - there were a few other laws passed at the same time...no one noticed till it was too late. I'm sure it's happening with the Marriage Equality Bill here in NZ as well (though, I'm invested in that one - it gives me the rights I am denied currently....) but the ones going through in the background whilst it is debated are a little concerning.
YOu cannot blame a persons sexual preferences etc for the dooming of the nation - it is the fixation with other people's lifes that is the dooming.