The worst thing that one can do is to react instantly and walk up on stage and question the MC.
We should reponse, not react.
Responding is different. Responding requires a cool, calm, deliberately structured and logical counter-argument that points out the error in the MC's comment. And in addition, let it be known to the public in a diplomatic way that I feel that the MC is wrong. In general, public members after reading a Response, would agree with the respondent, if his reasoning is sound.
Reacting, however, is simply a hot-headed huff and puff directed to the offending party (perceived to be offending by the offended person) with hardly any thinking. It serves only to create more problem. Never solve anything.
I will continue to do my job as a photographer for the event. Finish it off. Deliver my product professionally. Followed by an official letter to the organisation involved, cc to any higher authorities ONLY if there is no attempt to rectify the mistake.