A compiler flag is a blunt instrument. It affects all code the compiler touches, which may or may not affect code that you are intending to change.
Yes, such a compiler flag is a blunt and dangerous instrument and everybody should stay away from it. But everybody agrees on those points already. That's _not_ what you need to prove to show that such a flag shouldn't exist. What you need to show is that no-one will ever find them-self in a situation where such a blunt instrument would be useful.
