To play devil's advocate, he traveled to the U.S. with a guitar, had 5 shows booked in advance before his arrival, uses a pseudonym to perform and didn't declare any of this to the border officials. I think the article can also say he has a CD coming out soon. I can actually see why he was turned away. He's a musician, hoping to travel and do some shows in the U.S. for fun.
You can't work in the U.S. without a work visa. The rules are pretty clear about that.
Specifically denied is "paid performances, or any professional performance before a paying audience". If there was a cover charge to get in, it counts as work.
I think they vagueness of this points to part of the problem. There is no real specification of what makes an amateur performer in a musical event. I would assume since he was not contracted to receive a payment for his performance, it would be acceptable.
And just because there is a cover charge does not count as work. The cover charge is collected by the venue and does not mean he will get paid, which was specifically the case here.
Probably the guy broke a rule, or could at least be interpreted as breaking a rule.
However, the infraction is so minor compared to the penalty. The guy wants to travel around the country and play music for free at a variety of venues. He can't do this because that's considered work.
That really shouldn't be grounds for detaining, rough interrogation, strip searching and finally deporting the guy, all the while not allowing him to communicate with the people who are waiting for him.
Such rules really shouldn't be considered acceptable in a free and open country.
He's not performing at his Aunt's retirement home. He's getting on a stage in a bar, at a predefined date and time, with those dates advertised and promoted on his blog, in front of paying customers, entertaining them. Some musicians get paid for that, and some do not. He's hoping people will tip him or feed him. It's work.
You can't work in the U.S. without a work visa. The rules are pretty clear about that.
And performing for free is still work.