At least at the moment, Wikipedia has a pretty good page on how the interview went:
On February 21, 1989, Yusuf Islam addressed students at Kingston University in London about his conversion to Islam and was asked about the controversy in the Muslim world and the fatwa calling for Salman Rushdie’s execution. He replied, “He must be killed. The Qur’an makes it clear – if someone defames the prophet, then he must die.” 
Newspapers quickly denounced what was seen as Yusuf Islam’s support for the assassination of Rushdie and the next day Yusuf released a statement saying that he was not personally encouraging anybody to be a vigilante, and that he was only stating that blasphemy is a capital offense according to the Qur’an.
However on March 8, 1989, while speaking in London’s Regents Park Mosque, Yusuf Islam was asked by a Christian Science Monitor reporter how he would “cope with the idea of killing a writer for writing a book.” He is reported to have replied:
Well, Yusuf- may I call you Yusuf?-fuck you. And your prophet. You have have performed submission, but the rest of us haven't, and we still believe in that real Freedom of Speech thing. So fuck you and every sharia-loving asshole out there. You call for murder of someone for their words, and then whine that he was 'irresponsible' with his freedom of speech? You, sir, are a inflamed boil on the anus of humanity. So take your 'submit to sharia' shit, eat it and die.
In Islam there is a line between let’s say freedom and the line which is then transgressed into immorality and irresponsibility and I think as far as this writer is concerned, unfortunately, he has been irresponsible with his freedom of speech. Salman Rushdie or indeed any writer who abuses the prophet, or indeed any prophet, under Islamic law, the sentence for that is actually death. It’s got to be seen as a deterrent, so that other people should not commit the same mistake again.
Hey, we can say "It would be seen as a deterrent", couldn't we?