TWO WRONGS DON'T MAKE A RIGHT:

Way back in the past we used to have a very sensible saying that kept the peace within family units and the wider community. When ever a child was chasing a sibling around with murder on their mind, because of some "wrong" that had been done to them, a wise parental figure would take him or her aside and explain; 'just because Johnny had been naughty it didn't make it O.K to do whatever you want in retaliation'.
Now I think we could do with a resurgence of that type of thinking because it seems to me "responsible" adults have forgotten the basics of the premise. Just because a few of your army buddies get shot up whilst invading a foreign country doesn't mean you have the right to blow away a whole village of women and children; as happened in Vietnam in the 70's. Just because some bunch of crazies drive a plane into a building, doesn't mean you have the right to round up everyone with a tea towel on their head and torture them. Just because somebody kills someone doesn't mean you have the right to kill them. THAT is the way of Anarchy, and inevitably leads to a free for all or all out war.
It's bad enough that peaceful people have to put up with "terrorists" but then we have to put up with the maniacs who want to "retaliate" when the sensible approach would be to investigate before we run off half cocked and commit atrocities in the name of demon-ocracy. On the home front, it's not bad enough that we have to put up with "Serial Maniac's" but we have to put up with the hoards of CSI "Experts" who want to solve the problem by "Psychically Divining" the villain. Before you know it we will have a whole generation of "Freelance Dexters" running our "Justice System" and "Judge Judys" packing heat.
If you are of the mind set who thinks that would be a good idea, then I suggest you take a serious look at yourself and if you happen to get together with others who think the same then for goodness sake remind them of the good old saying that our sensible forbears used to quote 'two wrongs don't make a right