Question

which part of this excerpt from president Barack Obama's remarks on the buffet rule uses the logical fallacy of false dilemma​

Answer 1

Without having the excerpt here, I cannot say for certain, but I can help you to determine what it is.  A false dilemma is one that one uses to try to force an outcome by using an "either/or" situation.  For example, "One must either choose to pay higher taxes or choose to live a life in poverty."  So as you read  Obama's remarks, where is he putting that type of situation on that particular rule (the buffet rule).