That 30 second copy right rule is an urban legend. Totally not a real thing.
http://studentpressblogs.org/nspa/the-non-existent-30-second-rule/
Scott and the gang would be able to make a decent fair use case as this is technically music criticism, and using snippets rather then full songs would help their case. But if U2 really wanted to sue they definitely could. But they won't because the backlash wouldn't be worth it.