You can pose this question to all sorts of !@#$s. 
  
Christian !@#$s will respond with, "because evolution is an atheistic worldview that true Christians do not hold." 
Atheist !@#$s will respond with, "because creationism is stupid/illogical/irrational/whathaveyou, thus religion is stupid, and the theory of evolution proves it." 
Muslim !@#$s will respond with, "derka derka mohammed jihad!" 
Jewish !@#$s will respond with, "oy vey!  Saying the Tanakh is fallible?  It's shoah all over again!" 
  
Scientologist !@#$s will...well you get the point.