Why do theists insist that atheists aren't entitled to discuss religion?

Christians beleive that we should not discuss religion on this page because our ideas are so different from their own that by spreading the ideas of athiesm or non denominational belief we are jeprodising the ideas and ideals of christianity, something that they are trying to spread. It is a religious battle which started out as people expressing their ideas to others. This was a good idea until the christians started asking very anti athiest questions, using them as sick jokes, and trying to defame the ideas of the atheists as being ignorant ideas. Athiests have no say because they believe in a different truth