Some people are just doushebags like that.
Although, lemme throw a scenario at you:
~Paul is in the alliance "I Liekz Mudkipz" (MUD). They're ranked something like 15 overall and Paul's score and activity is far above the average score/activity rate of everyone else in MUD.
~Paul asks around to see if anyone else would take him, and the #6 alliance in the game says they would love to have him. This new alliance is very active and Paul fits into the average score of the alliance.
~He decides to jump ship.
Is that betrayal? Or would Paul have to attack those MUD peoplez first?
EDIT: I also have nothing against any Past, Current, or Future alliance with the tag of MUD and/or name which involves Mudkipz. I simply liekz mudkipz.