The threat is against British councillor Alan Craig who opposes a "mega mosque" that is being planned near the 2012 Olympics.
You can read the full story at the Daily Mail.
YouTube has a history of allowing Islamists to spread their propaganda on their site while making sure that conservative videos, and anti-Islamist material is taken down. Make sure you read this story about how terrorists are using YouTube for recruiting and propaganda.
So if you want conservative videos without dealing with the anti-American and liberal stance at YouTube then check out QubeTV.