He that would make his own liberty secure, must guard even his enemy from opposition; for if he violates this duty he establishes a precedent that will reach himself.

Thomas Paine
[The individual that values his the rights guaranteed by the First Amendment must also protect the rights guaranteed by the Second Amendment or everyone will discover the liberty secured by the 13th Amendment has been lost as well.

See also the nearly identical concept expressed by Alan Dershowitz.—Joe]