Question for evolutionists?

If one maintains that Darwinian evolutionary theory should be taught as fact, and at the exclusion of all other theories in public schools, one must subscribe to the notion of "survival of the fittest." If one believes that, "survival of the fittest," is a natural, evolutionary process, does the Endangered Species Act set a dangerous precedent in man's interference with nature? Wouldn't the artificially protracted preservation of a species destined for extinction result in an ecological catastrophe?