[Northern Monkey]

Looking at it objectively.
Yes it seems like a vile and nasty tweet.
However,If that was sent as a threat to someone i think Marc could get into serious trouble with the law for that and i don't personally think he would be stupid enough to literally threaten rape on Twitter.
I'd say on balance the likely hood it was sent to a friend who knows his sense of humour and they possibly speak like that to each other regularly is the more probable scenario here.
However,If it turns out to be proven to be a genuine threat then it is seriously ****ed up.