There are so many terrible assumptions in this quote its hard to know where to start.
First, just because Marx was an atheist, doesn't mean all atheists are Marxists. One can be Catholic and Communist, or Capitalist and Atheist, or any combination thereof. I'm not a Biblical scholar, but I'm pretty sure neither Adam Smith nor Marx are mentioned in the Scripture.
Second, and more importantly, why do religions people think that atheism lead inexorably to a life of despair and waste, devoid of any meaning? I think this is more a reflection of the religious man than the atheist. When they make this argument, really they are betraying their own views, namely, that their life would be pointless and they would be abject sinners if they didn't adhere to the Word. I find atheism to be actually quite empowering, since once one realizes that inherent meaning doesn't exist, one is free to discover one's own meaning.
To me, this argument is very similar to when people claim that we need religion as a way to keep our collective moral compass pointed in the right direction, as if it weren't for the Bible we'd all be larcenists, rapists and murderers. These people need to introspect, if that's what they truly believe.