Obama shakes Raul Castro's hand, so he's a commie. Haim takes a photo with David Cameron, so they're idiots. Since when did being polite automatically equate an endorsement?
To be fair, Haim's bassist, Este, ended their in-studio set by pointing at Cameron and saying something like "All for you, DC". I get where Johnny's coming from a bit in that regard, but it is complete over-exaggeration to say they're collaborating with the Prime Minister. She called him "DC"; if anything, she was being completely cheeky about it.