Man up and grow a pair
Anyone else bored with hearing this as a battle cry? The implication by the accuser ( not just you Dan ) is that the accused MUST - CLEARLY be in agreement, (I mean there's only one viewpoint right? - Yours), but for reasons of pure lily-livered cowardice is taking the opposite stance.
Ever thought that your colleague may have made a carefully considered cost/benefit analysis, trying to cut out the emotion because, ITS A JOB! in order to come to his opinion? Thought not....