Political records have been banned in the past .....& they go out live .......
The BBC has banned records because they disagree with the view being expressed, they weren't denying the artists' right to express their views through music. Music and politics are inherently connected.
This was a live event, and anyone could have said something which would have at any other time been unbroadcastable at any point. They should have cut the feed, and in hindsight they really shouldn't have broadcast Bob Vylan's set live, but let's stop pretending this is crime of the century.