No one questions survival of the fittest, it's arrival of the fittest that is rediculous. The premise that random mutation of an organism's DNA added all the components for complex assembly we call the human eye is preposterous. Multiply that by all of the complex systems in the human body, and the theory is just plain silly. The pinacle of absurdity, though, is the belief in abiogenesis.
X-men aside, mutation in DNA is almost never beneficial, and is at best neutral, but usually harmful.
Survival of the fittest is a tautology with no explanatory power, too.
But, you are right—abiogenesis is one of those things that makes you laugh out loud, until you realize they are serious.