It is correct that there will always be homicidal madmen. However, history shows that when ordinary people have legitimate grievances that are not getting peacefully addressed, they will often turn to support the homicidal madmen, seeing them as their only way out. This doesn't justify supporting the madmen, but this needs to be dealt with as a fact of life.
There is a story I think applies here:
My campus has an annual 'peace' event, with different organizations coming each year to discuss different solutions to the Israeli-Palestinian mess. OVer the years, it got almost entirely taken over by Communists, Socialists, and moonbats of all stripes, wearing black and red and chanting insane slogans.
Last time it happened, one group brought a former FATAH fighter to speak at their booth. It was a fattish, unshaven man with really bad Hebrew, drinking Coke from a 1.5 bottle and looking very uncomfortable in a crowd of college kids. In the stuff he said, there was one phrase that I remembered:
"We should all start behaving like responsible adults."
In a crowd of chanting, booing and jeering Communists it was the sanest thing anybody was saying.