That link from Maajid Nawaz (Quilliam Foundation) repeatedly says Sadiq Khan is no extremist, just that he was opportunistic in the past, standing alongside some unpleasant people in order to get votes.
Duh, typical politician.
Let's give Sadiq a fair chance as London Mayor
I disagree with IPityThePontipines about Quilliam though:
They are a Muslim thinktank / lobbying org which produces ideas that are controversial to many other Muslims - such as stopping public funding to more fundamentalist groups - but that does not make them irrelevant or useless to the country as a whole.
They advocate a more liberal Westernised form of Islam and discuss how best to oppose extremism.
They usually seem most comfortable among the Liberal Democrats, but Nawaz waited until after the election to say he voted for them rather than Sadiq Khan.
Policies generally mainstream liberal too:
They have defended the rights of women to wear the hijab or the burqa, but also not to wear them.
They have condemned Israeli actions in Gaza, but not the right of Israel to exist as a state.
They have confronted racists like Geert Wilder and the EDL - and managed via discussion to persuade the EDL leadership to stop street protests.
btw, they have received no public funding since 2011, when they disagreed with government policy.