Then I should just throw away my copy of the Federalist Papers despite their explanations and thinking of the day of the proposed Constitution?
Hardly. But you decide what the Constitution says based on the words in the Constitution. Not by ignoring the words there in favor of some other source.
Here's what Scalia had to say:
“Even beyond the unreliability of almost all legislative history...as an indication of intent, it seems to me that asking what the legislators intended rather than what they enacted is quite the wrong question."
"Statutes should be interpreted, it seems to me, not on the basis of the unpromulgated intentions of those who enact them...but rather on the basis of what is the most probable meaning of the words of the enactment, in the context of the whole body of public law with which they must be reconciled."
Scalia Speaks- Reflections on Law, Faith, and Life Well Lived Antonin Scalia