IIRC he didn't call everyone who intends to vote against the air strikes a 'terrorist sympathiser', he implied
some of them are terrorist sympathisers, based on their previous comments I believe. It wasn't the first time he'd done so either:
http://www.ibtimes.co.uk/british-pub...attack-1523040
and I don't recall the same level of 'outrage' then...
It was still unnecessary, however, and a major distraction from a hugely important issue however, since it would obviously be used as a stick to beat HMG with.