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Two quotes by Abe Lincoln stand out about this:
Our defense is in the preservation of the spirit which prizes liberty as the heritage of all men, in all lands, everywhere. Destroy this spirit, and you have planted the seeds of despotism around your own doors.
Speech at Edwardsvill, IL, September 11, 1858
At what point then is the danger to be expected? I answer, if it ever reach us, it must spring up amongst us. It cannot come from abroad. If destruction be our lot, we ourselves must be its author and finisher. As a nation of free men, we must live through all times, or die by suicide.
Young Men's Lyceum Address, January 27, 1838
The party of law and order are shooting up their opponents. This is where we are now. >

They will not stop. 
We are well past the point of justifying self-defense.