This is in danger of mixing issues and stoking hone-grown racism.
Certainly, there's a lot wrong with Sharia, and with Beth Din, and with "ecclesistical" courts in general. We don't need bearded weirdos making laws and running gaols, like we used to have.
So any embrace of Sharia, or other religious law must be voluntary, and within the parameters of ordinary civil and criminal law. But if people want to use religious institutions to mediate in disputes, make the decision freely, and this is done within the regular framework of the law, then it's no-one else's business.
Unfortunately, this group seems to lump the "Sharia" of the North-West Frontier with UK practice. I think this is intended, militant secularism is their thing.
A tolerant society cannot in all conscience legislate against vicars and the like arbitrating in disputes, if both parties want that.