Oh, come on! Just because someone isn't interested in the opposite sex yet doesn't mean they are immature in that sense of the world. They're just at a different stage of development, and the "eww, boys are gross" point of view is perfectly natural at that age.And this is coming from someone who is doesn't even like the opposite sex yet.
And you call us immature.
And it is true that boys generally take longer to become mature (in behaviour etc), so the poster was correct. There's really no need to name-call.