I feel sexual sin is one of the worst sins there is. but it is also a very hard sin to understand especially these days. Some people will say to me, well what about my parents, they arn't in the church and they had sex when they were young so your telling me they are bad people?
I guess what we individually have to be aware of is our own knowladge. A bit like when we were little kids if no one told us to not put our hand in the cookie jar then we wouldn't have known any better
However we, as later day saints, DO know better and the world would be a lot happier place if it also did.
Think about a world that follows just that one standard no sex before marriage! What a happier place it would be! No teenage pregnancies. Lack of STDs (or even non)! Family units would be a lot more secure.
I personally feel sexual sin is like a plague and is spreading. Pornography, adultery and worser still devastating acts such as child abuse.
The world sure needs its savior and I have great faith that this world won't have to wait much longer.