As I understand it, it boils down to logical consistency.
the statement "X is universally preferable" means that all people, at all times, want everyone to do X
So if we have 2 people in a room, they are both ok both with doing X, and having X done to them.
The problem with some X's is that if you want X done to you, then its no longer X, thats where the logical consistency comes in
If X = "watch TV"
I can want you to watch TV, and that doesnt change what watching TV means, if you watch TV you are not both watching and not watching at the same time.
If X = "stolen from" then
I can want you to steal from me, but then if I want you to steal from me, its not stealing , because I am giving you permission to take my possessions. You would be stealing, and not stealing, at the same time.
So the test for morality is, does the definition or understanding of X change, when I want you to do X. If it does its immoral.