OR why you shouldn't elect a bully class president.
The argument is simple; no sane person should hope to be led by a group of people who are willing to use violence against civilians to make a political statement. None of us wants to be the target of a random violent attack and you don't know what new ends might justify your murder.
For example, the Palestinian people hope to establish some form of government when they do gain independence. Leaders of nationalist movements often play crucial roles when they have attained their objective (independence in this instance). In many cases, their struggles prepare them for future positions of power. Someone who leads a peaceful resistance or protest movement learns how to organize people with different interests, use media to further their interests and give strength to the wavering while honing their rhetorical skills and testing their own dedication to the cause. Martin Luther King Jr., Mohandas Karamchand Gandhi, Nelson Mandela, Vaclav Havel led movements to accomplish radical change and did it without resorting to egregious violence. In the process they developed abilites that made them effective administrators and leaders of organizations and people. They also learnt how to gauge the interests and true motivation of their communities and convince, occassionally winning over their opponents by sheer dint of persuasion.
What skills exactly, does the leader of a terrorist group learn that would be useful after the objective has been attained? They learn how to run clandestine operations and acquire the means to cause widespread havoc and destruction. They become masters at convincing gullible young men and women to put their lives at risk and kill and maim innocent civilians. They learn to reject compromise and belittle negotiation. Perhaps worst of all, they convince themselves it is permissible to use force against bystanders as a means to attain a political end.
None of these abilities prepare them for public life in a non-totalitarian state. There is little use for such people in the military or police of a republican or democratic nation, since it dangerously undermines the civilian government. Unless you see Adolf Hitler, Josef Stalin and Pol Pot as ideals, you would wish for a pacifist as head of an autocratic state. Leaders who have washed their hands in the blood of innocents are not fit to lead a community that hopes for a prosperous peace. Everything they learn in their struggle corrupts and taints them, leaving them unfit to participate in peaceful government. It is best not to let your cause be undermined by their means. These aren't people you want around when the fighting's over, so avoid them from the very beginning. Reasoning individuals should never support the call "by any means necessary".
This may sound painfully obvious to you, but there are still people putting up posters of suicide bombers, egging on the IRA, giving to the Khalistanis/LTTE, watching their propoganda approvingly, while extolling their bravery.