Sorry, I cannot agree that the three stabbed men did the right thing.  In my book the man doing the mouthing off was insane.  Insane means unpredictable and not likely to act as sober rational people will do.  Is it wise to approach a foaming rabid growling dog?  The men had good intentions but followed a defective pathway.  We can expect more deaths if folks attempt to intervene against crazy rants by the insane.  It would have been different if the insane man had actually attacked anyone (and I don't mean verbally).  Then the men would be unquestioned heros who gave their lives to protect their fellow citizen(s).  As it is, the men with the best of intentions did the wrong thing.  Provoking a rabid dog is not a good thing in the sense that it can lead to death.  In the future, folks might wait, make a call to police, attempt to defuse the situation non-violently by encouraging others to exit the bus or talking to the driver asking him/her to stop the bus and get passengers off, etc.