Wait what? Why? Really? C'mon.
So manning a 1,000+ kilometer border is the best idea to this nebulous problem?
Existing border patrols and law enforcement agencies already do a good job of keeping out moronic criminals and/or political violent nut jobs.
Dedicated and trained thieves/spies/terrorists/freedom fighters would simply bypass and/or avoid such blatant security measures. To them this fence would be a joke. It would also mean re-directing good government money that could have been spent on better, more sensible security upgrades. Like a 'busboy' with a suppressed pistol who plans on popping a bad guy in the head when the baddie visits a certain Paris cafe.