I hate ponies because it is a group of people thinking they are cool by liking such a childish thing, and they do not really like it, they just say they do so they can be part of the cool little group of the MLP fans. This makes them feel complete as they are accepted in a group.
Yet it can be argued that the people that do not choose to be in it want to be in the Anti-MLP group and therefore feel complete, but this doesn't really apply because then the group would include people who never heard of MLP.
Comes down to people wanting to be part of a group.