People are jumping to his defence not for his message, but his right to say it.

But that´s the core of freedom of speech, even if you don´t like it or find the lyrics terrible (I have not heard the song). As long as they are not plagiarising or illegal e.g. promoting a crime, they should be allowed. Even propaganda should be allowed. It is in fact allowed, I have never seen censoring of anti-isreal propaganda, did you?