If the news coverage of this incident is to be believed
"the passenger was drunk and abusive prior to boarding the flight"
A question must be asked of the ground staff as to why he was allowed travel.
It may be easier to board the passenger rather than risk confrontation at the gate but, as has been demonstrated the results of putting a drunk abusive yob in a confined space for a protracted period of time, risked the life of a member of the crew. Had he in his rage reached the flight deck who knows what the result would have been.
Its time to take action at the boarding gate and not allow the possibility of anyone who is drunk to board. If it is suspected that by taking this action a fracas may result, the authorites are only a phone call away.
Lets keep the trouble on the ground where its easier to deal with.