I could make a rule-utilitarian argument for why authorial control is a good principle, but honestly my position is more deontological. Reason is the slave of the passions, all ethics discussion must bottom out in human instincts, so my only real argument is that most people seem to think this is a good rule: it's widely accepted that the author of a creative work should have a lot of control over how that work is reused. Most countries have copyright laws that let a creator control the production of derivative works; many go beyond that and have non-transferrable "moral rights" that let the author control derivative works more strictly than intact copies of their original work. Even the FSF, largely anti-copyright, gives the author options to strictly control how their work is presented in the GFDL (e.g. invariant sections).