This sort of organisation is nothing new. For example, there's
NAMBLA in America.
As with many things, I strongly disagree with their views, but I respect their rights to say it.
They do have a point about the concpet of an "Age of Consent" being too arbitrary, as inevitably, it will be too high for some people, and too low for others. As it is, there is no better way to judge maturity so we must err on the side of caution (a too low AoC is much worse than a too high one).