The quote below was written by U.S. leader George Kennan:
Now it lies in the nature of the mental world of the Soviet leaders, as well as in the character of their ideology, that no opposition to them can be officially recognized as having any merit or justification whatsoever. Such opposition can flow, in theory, only from the hostile and incorrigible forces of dying capitalism.
What does this quote justify?

The stated quote was written by George Kennan, a Foreign Service Officer. The policy of containment post the Cold War was formulated by Kennan in 1947. the policy of containment was formed to fight against the Soviet Union with the allies.

Post the Cold War, Soviet Union became an isolated country behind the iron bars made by Joseph Stalin. In response to Stalin's foreign policy, Kennan wrote an 8,000-word telegram as Mr. X to the Department.

The given quote justifies this containment policy only formulated by Kennan in 11947 in response to Stalin's foreign policy.