The "teach both"-argument doesn't hold. Time and resources are limited, the same applies to education. Choices must be made, in this case on a scientific basis. Diversity of views in education isn't paramount: Should education about the holocaust be "balanced" by also teaching theories of holocaust-denial? No of course not. Science and facts (historical accounts) clearly favors the view that the holocaust did occur above the nutjob-theories that deny it. The same goes for evolution vs. creationism.