I have a problem player similar to the guy you are describing. Long story made short, giving him room and being reasonable has lead to more problems and other players left without saying anything rather than deal with a confrontation. I only recently became a dm, so the other dms share the blame, but I regret all the chances we have given. We even suspended him for two weeks and gave him a list of written rules, and he was ok for a while, but he just had two outburst in two weeks so I now want to ban him from my game and I lost players by trying to work with him. Take my advice, be firm and fair and fix it now or have him sit this campaign out
