In the next sentence you say people will never tolerate tyranny.  I would suggest, given the reality that many people on this earth are forced to endure tyranny, and endurance is de facto tolerance, that people should never have to tolerate tyranny.  It is the obligation of those who are free to help those who suffer tyranny. 

The means of help are many.  Reagan did so by spending extraordinary amounts of money on national defense, forcing the Soviet dictatorship to follow suit, and they ran out of money before we did (most likely result, but not an absolute given -- quite a gamble).  Personally, I think instead of building more, bigger sticks, we could have grown many sweeter carrots to the point we could have simply given some away to entice the people of the Soviet Union to give up on and walk away from their government.  We could do the same for Cuba if we so chose.  And Afghanistan, and Myanmar, and ...

There are too many people, who are too easily swayed and divided to expect that we will all naturally tend toward a cohesive, peaceful world union.  Chaos theory, the concept of entropy, many things point to our heading not toward unity but toward fragmentation.  It takes a concious realization that we want to unify, holding dear to ourselves the knowledge how and why to do this.