a) violence is committed by people. so: get rid of all people b)
  violence is committed by some people: so, remove some people. c)
  getting rid of people is wrong. So, change the violent acts. d)
  how do you change the violent acts? You can stop them as they
  happen by monitoring actions and preventing as they occur. e)
  But as they happen isn't soon enough? Then you stop them before
  they start. f) But how do you stop people from committing
  violence before they do it? h) What do they commit violence
  with? Remove the tools they use. i) What tools are used for
  violence? guns? bombs? Can you remove them? j) You can make
  laws. But not everybody follow laws. k) You can restrict
  commerce. But not everybody follows commercial routes. l) So,
  you monitor everybody to make sure they don't have tools for
  violence. m) But what about making their own? Can you restrict
  parts? n) Violent tools follow the laws of physics. Can you
  restrict the laws of physics if someone builds a weapon out of
  fertilizer, ammonia and a box of nails? o) So, while perhaps
  some help, gun control can't fully solve violent acts. This
  doesn't mean it's not valuable but it's not a total solution. p)
  So we'll continue: If you can't restrict the tools used... maybe
  you can stop the people from getting to the areas you are
  protecting. q) Ok, you close the borders. But what if they're
  already inside? r) You monitor everybody. But for what? What can
  you monitor them for? == Quite true. Back in the 1980s, when
  terrorism was usually cubans stealing a plane and demanding
  ransom or something, head scarves were banned in my mother's
  workplace. She worked for the local government in their justice
  system. No native Muslims complained. That was just how it was.
  Government office. Separations of church + state and such. A
  couple of American black muslims did but this was an era of
  racial quotas for hiring. Affirmitive action has improved
  GREATLY since then, but it was in its raw form then. The thing
  is: They ALSO banned Jewish headgear. Lots of Lawyers were
  jewish. In short, outside of a few rabble-rousers, nobody
  complained about the restriction. But France? I don't know if
  they restricted all religious displays on heads or just the
  scarves. But if it was just the scarves? Yeah, that's pretty
  bad.