Because of anti-Islam sentiment. Which is fine, it's their radio station and the first amendment only applies to Congress but here's the part that gets me:
Subject: Notification for Richard Dawkins: Science in the Soul: Selected Writings of a Passionate Rationalist
Dear Richard Dawkins event ticket buyers,
We regret to inform you that KPFA has canceled our event with Richard Dawkins. 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. KPFA does not endorse hurtful speech. 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. Your ticket purchases will automatically be refunded by Brown Paper Tickets.
Sincerely,
KPFA Radio 94.1 FM
"We emphatically support free speech just not, you know, the upsetting kind. Or the not-serious kind." What is "serious" free speech anyway? I'm pretty sure Dawkins was being serious when he said Islam is the biggest force for evil in the world today, that this is a belief that he sincerely holds.
Why do people say this? Why not just say "damn straight we're no-platforming him because he's a hateful Islamophobic bigot".
I don't think anyone really supports free speech so why not just dispense with this "we support free speech just not your kind of speech" nonsense?