Why is the 'left obsessed with suppressing freedom of speech?

It seems the pro immigrant BBC tried a little stunt and it back fired, good! i see in the article the BNP weren't asked to participate or defend themselves but they thought the majority of the calls would be anti BNP, how wrong they were. The left are just a bunch of self righteous bigots who refuse to understand people have their own opinions and don't appreciate being lectured to by people about other peoples plights that don't affect the person lecturing or being lectured to.