Mutsy - I think it was different world back then. In 1947, when Truman was President you had Stalin as the leader of the Soviet Union who was ruthless in his attempt to spread communism to other countries.
This animosity continued throughout the Cold War, but it finally ended as a result of President’s Reagan active stance against communism.
He not only provided aid to anti communist forces within Latin America and Afghanistan, but he created an arms race with the Soviet Union that bankrupted the Soviets and caused the economy to collapse and communism to cease right along with it.
The difference between the Truman Doctrine regarding communism and the Reagan Doctrine was that the Reagan Doctrine went a little further and took much more active measures against communism.
President Reagan was not interested in containing communism. His interest remained in destroying communism where ever he could.
He did not trust people that held communist beliefs and realized that they were the enemy.