but these imams were muslims, and the parents of the girls were muslims, and their extended families were muslims. Therefore, some muslims in the UK knew about it.
Precisely, and exactly, the same could be said of the 7/7 bombers. The imam of the Birmingham Central Mosque, who is most certainly not a fringe player in a semi-detached house, still claims that 7/7 was an inside false flag job done to discredit Islam (his views on 9/11 are sufficiently vile as to not be repeatable). What do I deduce from this? That Muslims I work and study with all secretly want to blow me up? Don't want to blow me up, but are indifferent if someone else does? What?
Of course, just to complicate matters, Samantha Lewthwaite's extended family certainly weren't Muslims, but let's not let that stop the general purpose racism of your position. They're brown, right, so they must be up to no good, and the ones that aren't obviously up to know good need to prove that they're not secretly plotting, eh?
can't muslims try to convince other muslims that forced child marriage is unislamic?
Perhaps more Christians should have devoted effort to convincing Peter Sutcliffe that Jesus was not, in fact, telling him to murder prostitutes.