It is not of God to say “this is a word from the Lord” when what you say are merely your own words. “God is against you” if you practice that.
Part of the mission of Christ’s followers is to teach the way of Christ – and to warn when someone is teaching “another gospel” different from what was written by the faithful early church. “Warning” about false teachers and false teachings — is a good thing we do. It is what “a good servant of Christ Jesus” does.