You know, there was a time when musicians appeared in movies, did TV shows and it was fully expected. Frank Sinatra, Elvis, Bing Crosby, Sammy Davis Jr., Sonny & Cher, Judy Garland, Dean Martin, even the Beatles - it was expected for them to not just sing and have big hit records, but to make movies, be on TV with their own show or make appearances on TV shows, etc.
Then, somewhere along the line, things changed. Suddenly even daring to appear in a movie or have a script about a certain artist meant that the artist "sold out" and was "cheap". Oh, that makes sense... So now U2 are responsible for a storyline about them? If that's true, what about all the other times U2 have been mentioned on TV or the movies? All those were cheap too? Should no U2 songs ever appear in a movie? Should U2 just do music and nothing else? Should they sue any time anyone even thinks about uttering the word "U2" in public?
Somewhere along the way, people's attitudes about musicians changed - I think it started in the late 60's. Ironically enough, even acts like Hendrix, the Doors, Joplin, etc., all appeared on TV. Did they sell-out too?
Well, I don't buy it. Musicians are entertainers, and if they can act, dance, write, go solo, whatever, they should do it.
Bottom line - U2's concert went on as normal, with one tiny sentence that probably no one at the show got (or even heard) accept for those actors. Given that Mark Wahlberg is the producer, a man who knows about entertaining (and is a far better actor than musician), I see no problem with U2 doing this one tiny thing. Plus, we got to see a bit of the concert.