Evolutionary biologist Richard Dawkins has denied Islamophobia after a US radio station cancelled his forthcoming speech.
The best-selling author had been due to address an event hosted by KPFA Radio in Berkeley, California, in August.
Organisers accused him of "abusive speech against Islam" when scrapping his appearance, an allegation he denied.
He called on the station to review his past remarks and apologise.
In a letter to ticket-holders, the publicly funded radio station wrote: "We 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."
The station, which is not affiliated with the University of California, said in a letter - which Mr Dawkins published online - that it does not support "hurtful" or "abusive speech".
It also apologised "for not having had broader knowledge of Dawkins views much earlier".
Local media report that Bay Area residents had brought attention to statements made by the author of the anti-religion book The God Delusion, including a 2013 tweet saying "Islam is the greatest force for evil in the world today".
In an open letter to organisers, Professor Dawkins wrote that he "never used abusive speech against Islam".
He said harsh statements he has made in the past have been directed at "IslamISM" - apparently referring to those who use the religion for political objectives - and not adherents of the faith.
"I have criticised the appalling misogyny and homophobia of Islam, I have criticised the murdering of apostates for no crime other than their disbelief," Professor Dawkins writes.
He also pointed out that he has been a "frequent critic of Christianity but have never been de-platformed for that".
He describes listening to KPFA "almost every day" during the two years he lived in Berkeley, adding that "I especially admired your habit of always quoting sources".
"You conspicuously did not quote a source when accusing me of 'abusive speech'.
"Why didn't you check your facts - or at least have the common courtesy to alert me - before summarily cancelling my event?"
Professor Dawkins' book about the study of evolution, The Selfish Gene, was named last week by the Royal Society as the most inspiring science book of all time.
Known as the home of the Free Speech moment in the 1960s, Berkeley has recently left that reputation in doubt as far-left protesters have sought to silence speakers and academics with whom they disagree.
Conservative authors Ann Coulter and Milo Yiannopoulos have each clashed with the University of California after events where they were due to speak were cancelled by the college administration out of fear for public safety.