The slang term has two meanings in the U.K. and U.S., respectively. When a Brit calls themselves "gooners," they are emphasizing their support for the Arsenal Football Club. However, Americans refer to "gooners" as impulsive pornography addicts who are known to be chronic masturbators.

This is a non-story. He was addressing Parliament. Why would the US meaning be at all relevant when the UK PM addresses the UK Parliament?