B because it is “pulling” someone away from their home land, making it a pull factor
Eisenhower believed that it was very important to keep a non-Communist government in Vietnam. It was believed by many at that time that Communists all over the world were united in a international conspiracy and their plan was to topple non-communist governments one by one until they achieved world wide domination.
He supported it because he believed that the powers enumerated in it balance each other out and nobody could become tyrannical by exploiting it. He refers to it as an open door because it can be amended meaning that if something needs to be changed because the spirit of the time has changed, it can be done while keeping the good things.
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