The problem is not that the British Chamber of Commerce is in favour of staying in the EU and suspended John Longworth because he disagreed with that stance which is how the Daily Mail presented it.  The BCC had actually voted to retain a neutral stance on the referendum and to not comment on the arguments being presented by either side.

John Longworth broke that policy decision - if he didn't agree with the neutral stance of the BCC then the honourable thing to do would have been to resign before making his position public - he certainly shouldn't have used an invitation to speak as head of the BCC in order to make his point.