1. Matthew 18 establishes a procedure for dealing with personal sins not public debate
2. Just as private matters should be handled privately public matters should be handled publicly
3. When an author has confessionally submitted to a church writings that impact the application of the standards and polity of said church are public rather than private matters
4. Teaching, preaching, and publishing entail putting things in public that invite public enquiry and criticism
In other words, once you go on record you can be asked about or criticised for anything you've said on record. Phillips is referring to a specific dispute that you may not have heard of (or care about) but the bullet points may be applied across any number of situations.