Exactly what in Galatians do you see as a rebuttal?
Pretty much the whole book.
Apparently you're not familiar with it, but if you were to read it with an open heart and mind, you would find that Paul rebukes those Christians who once had the freedom of the Spirit, but who are now reverting back to legalism as a way to maintain favor with God.
Galatians 3:24-25 -- The law was our schoolmaster to bring us unto Christ, that we might be justified by faith. But after faith has come, we are no longer under a schoolmaster.