Two wrongs do not make a right.
As odd as this is going to sound, I disagree. A simple blanket statement that makes no allowance for corner cases? I'm going to need something more than that to be convinced.
Let me explain...
In this particular instance, the "wrong" of hogging bandwidth is far, far greater than the "wrong" of blasting the hogs into oblivion. Even though privately-owned and run, one should expect at least some sense of common courtesy when using a resource like wifi. If you want to download pr0n and/or ripped movies, for heaven's sake do it at home and pay for the pipe. There are very few legitimate reasons to run multi-GB BitTorrents at full-bore in a coffee shop, and I promise you that there are simply not that many people who desperately need an emergency .iso download of CentOS or Ubuntu away from home.
Certainly, the guy could get a hotspot (as suggested), but that's like telling the guy to go buy his own property if they want a quiet park to sit in when a small group in the public park has a constant loud party going on. Also, hotspots don't always work as advertised - I lost count of the times I've had to duck into a rural/small-town MickeyD's or coffee shop because the stupid employer-issued hotspot/3g/4g device didn't have enough bars to get a decent connection.
Maybe I sound like a dick for cheering this guy on, but think this through for a moment - if coffee shop owners start getting slammed with MPAA/RIAA C&D orders, if their costs skyrocket, and if they generally figure the wifi to be more trouble than it's worth, then eventually the "free" wifi will become metered, will be QoS'd down to practically nothing, or worse. None of us want that. I like knowing that if my normal connectivity goes tits-up, I can duck into a coffee shop, buy a cup of joe, and use their wifi to do what needs done until I can get connected normally again.
It's abusers of the system that eventually become the reason why we can't have nice things, so this little "wrong" is a pretty nice way to keep bigger "wrong"s to a minimum, no?