The violence in this country has come from both the left and the right extremists.
On the world scale, in the last century the horrible massacres came from the Nazis and the Marxists.
They get out of different sides of the same bed.
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Islam has been trying to conquer the West for over a thousand years.
Some see this as their religious duty, and martyrdom a quick path to heaven.
Mass immigration is the new weapon.
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Just because you have one kind of problem (domestic terrorism) does not mean that you should not try and prevent another kind (Islamist terrorism).