That's backwards. For those who consider contraception an evil, it is the symptom of moral decay, not the cause of it.
If the moral decay wasn't already happening, contraception would not have gotten a foot hold.
Evil cannot gain a foothold where is it not allowed.
Contraception is an easy thing to hang one's hat on to blame the state of the world, instead of taking personal responsibility for our own contributions to the decadence of this planet.
Blame-shifting is always easier than doing something about it and feels so much better.
Or we can talk about abortion...........
“Among the religious institutions of national influence, the Catholic Church stood alone in protesting the immediate evil and long-term implications of Roe v. Wade . Although it is largely forgotten today, evangelical Protestantism was in support of Roe v. Wade”.
http://www.firstthings.com/web-exclusives/2007/01/thirty-three-years-after-roe-v