The writer has justified his comments asking why the radio station thinks it's fine to criticise Islam and not Christianity.
KPFA Radio in Berkeley said they "had booked this event based entirely on his excellent new book on science, when we didn't know he had offended and hurt - in his tweets and other comments on Islam, so many people. KPFA does not endorse hurtful speech".
An example of the comments they were referring to was a tweet sent on 1st March 2013 from Dawkins saying "I think Islam is the greatest force for evil in the world today. I've said so, often and loudly".
The radio station wrote in a statement: "while KPFA emphatically supports serious free speech, we do not support abusive speech. We apologize for not having had broader knowledge of Dawkins views much earlier. We also apologize to all those inconvenienced by this cancellation."
They also suggested that it was complaints from community members that led to their awareness of his views on Islam.
In an open letter on his website, Dawkins does not apologise for his comments.
He explained: "I have called Islamism "vile" but surely you, of all people, understand that Islamism is not the same as Islam and maintains that it has 'oppressive cruelties''.
Dawkins added: "I am known as a frequent critic of Christianity and have never been de-platformed for that. Why do you give Islam a free pass? Why is it fine to criticise Christianity but not Islam?"