Marcus himself has re-Tweeted a couple of examples of the abuse and threats he's received. I'm not posting the actual abuse, due to the NSFW language, but it can easily be found online.
But, next time your team concedes a penalty that you can't bring yourself to admit may have been deserved, think a second or two before posting a red-mist tirade. Otherwise, you're on the first step towards this sort of behaviour yourself.