Dinesh D'Souza, in his recent debate (youtube) with Christopher Hitchens, complains,
We live in a very unusual time in which atheism has emerged as a kind of militant phenomenon. On the face of that, it seem a little bit odd, because if you are an unbeliever, why be militant? I don't believe in unicorns; but, I haven't written any books on the subject. I don't spend a lot of time denouncing unicorns; I live my life as though unicorns did not exist. But what we have from the atheist side is a belligerent attack on theism and specifically on Christianity.
D'Souza is right that both god and unicorns have the same likelihood of existing.
But the difference is that belief in god informs the politics and ethics of many people. It creates unnecessary suffering and division.
Belief in unicorns does not necessitate any (im)moral precepts. Unicorn believers don't hijack government resources to further their supernatural world view nor fight to prevent access to contraception and abortion.