Yeah, its a bit shit. Looking over the britishoppression site, there is no mention I can see of their seeking 'to fight for the establishment of Sharia law [throughout Britain]'. I can well believe it is part of their overall agenda, but it isnt actually stated as such. That makes me a tad suspicious of the rest of it. One bit of lazy writing is okay, (at least) two, and it's not unreasonable to start getting a bit suspicious.
Also, I do wonder how what will be a very probably be an overwhelmingly white counter-demo would go down amongst the demonstrators - especially as the ostensible reason for the demo is not entirely unreasonable (as the call out accepts)