Protagonist-Centered Morality: Vampires converting humans into more vampires without their consent - bad. The Fae converting humans into more Fae without their consent - good. A very clear-cut example of the trope, since in any other circumstances, aliens from space who acted in this way would be the villains, but because these aliens are our 'heroes' their every action is treated as benevolent and reasonable.
Vampires are fundamentally different people than the humans they are made of and explicitly not the same soul, FAEification does have some worrisome mental effects what with the muscle memory, but seems to every human test to not affect the mind and even preserves the soul as seen with the converted Slayers.
Science Marches On: Recent experiments by NASA into the Electromagnetic Resonance Drive seem to suggest that reaction mass is not as fundamentally necessary for space propulsion as previously thought. This casts the optimized ionic propulsion used by Fae spacecraft as unlikely.