The American Idiot singer was in rehab tackling substance abuse issues as Psy took over the world's charts with his catchy dance anthem last year (12), and now the Asian superstar is back with his Gangnam Style follow-up, Gentleman, Armstrong has taken to his Instagram.com page to fire off at the wacky star.
The punk rocker writes, "This dude is the herpes of music. Once you think it's gone, it comes back. #herpes #flareup #pleasegoaway."
Armstrong's feelings aren't echoed by all snarling rockers - former Oasis frontman Liam Gallagher recently revealed he's a big fan.
In a web chat with Japanese fans in February (13), the British rocker was asked if he liked Psy's break-out global hit and said, "I think it's an absolute classic. I love it. My kid dances to it every morning and it makes me chuckle and spit out my Corn Flakes."