Nature of the beasft, people come, people go. So to speak, or in this case type. We all have to find that niche in which we feel comfort and as it may feel as disloyal when one leaves, it is comfort they may seek.
So be it, we shouldn't treat them differently because they choose to seek comfort elsewhere. We should rise above ourselves, it js only a game. Friendship gained may feel lost but friends will support a friends decision.
Just saying.