So, the short version is some anonymous guy may have said this crazy thing. Maybe that happened. In Islam there are no priests and anyone can study the Koran then issue an opinion. But there is a lot wrong with this starting with the fake name, which translates into something like the "bloody butcher".
Nothing is binding about this supposed position. Kinda like a deacon at a local church saying Jesus does not want race mixing. Sure the deacon could say that, but it will not be believed or adopted by the parishioners.
So there is no way to authenticate that this is an actual Shiite cleric in London, say as opposed to a complete imposter?
I don't know? He is supposed in be in London, but all references that Google finds are related to this. In any case a fatwa is the opinion of someone who has had some religious training. But it is nothing like an official rule. Each cleric, be he a mullah, or imam or ulama; has strength based on how many followers agree with him. Because of this you get all sorts of crazy fatwas.
So I have no idea whether this is a hoax or not, however there are a lot of red flags:
1. Unknown anonymous cleric
2. Likely fake name
3. *First appearing on a propaganda website
4. Shocking and hard to believe statement
*Here a just a few MEMRI board members and board advisers.
Oliver "Buck" Revell: Chairman; Former FBI Executive Assistant Director
Donald Rumsfeld, Former US Secretary of Defense
James Woolsey, Former Director of Central Intelligence Agency
John Ashcroft, Former US Attorney General
Paul Bremer, former Director of Reconstruction and Humanitarian Assistance in Iraq
Deborah Lipstadt, Dorot Professor of Modern Jewish and Holocaust Studies at Emory University.
Natan Sharanksy, former Israeli Minister for Jerusalem and Diaspora Affairs