I have argued more than once that toleration has limits. See, for example, The Danger of Appeasing the Intolerant and other entries in the Toleration category. I am pleased to see that the astute Charles Krauthammer has argued something similar. He calls his position "situational libertarianism":
Liberties should be as unlimited as possible — unless and until
there arises a real threat to the open society. Neo-Nazis are
pathetic losers. Why curtail civil liberties to stop them? But when
a real threat — such as jihadism — arises, a liberal democratic
society must deploy every resource, including the repressive powers
of the state, to deter and defeat those who would abolish liberal
democracy.
Civil libertarians go crazy when you make this argument. Beware the
slippery slope, they warn. You start with a snoop in a library, and
you end up with Big Brother in your living room.
The problem with this argument is that it is refuted by American
history. There is no slippery slope, only a shifting line between
liberty and security that responds to existential threats.
Krauthammer mentions Lincoln's suspension of habeas corpus during the Civil War and FDR's internment of Japanese during World War II, and points out that after the crises were resolved, liberties were restored.
It is worth noting that there is no logical necessity that one slide down any slippery slope. One can always dig in one's heels. Slippery slope arguments are one and all invalid. But there is more to argument than deduction, and so the topic is a large and hairy one. See Eugene Volokh, The Mechanisms of the Slippery Slope.