I cannot agree with this. Singers can have political views but they should not talk about them when they perform. I once saw Hugh and cry at a festival. The singer did nothing but preach his politics the whole way through their set. I didn't care much for them before but absolutely detested them afterwards. If a singer has strong political views he/she runs the risk of alienating some of their audience.
It's rather like Rod Stewart coming onstage in Glasgow wearing a Celtic strip. He nearly caused a riot, then said oh, I didn't realise it would cause so much trouble. You wear any colours in any city and you immediately cause a divide.