I contest the arbitrary assignment of the 'evil' designation to undead dragons.
In fact, I argue that undead dragons are actually the fantasy-equivalent to singularity-people in sci-fi. Thus, they are liberal, progressive, forward-thinking dragons. Who have made an effort towards sustainability (they consume far less energy and don't need food).
So clearly, them being 'evil' is entirely rooted in dogmatic hogwash.

Let's have tolerance.