The guy has an interesting perspective, but he's a bit off base in his conclusions. Granted, UV purifiers are not perfect, they have their downsides (as do the other treatment methods), but they have significant advantages as well.
It really depends on where you are at. Maybe I just haven't encountered that situation in the Western States where I frequent, but in 40 years of hiking I've never had to purify or filter truly murky water, even from lakes. If I did, I would pre-filter it, but I've always been able to select relatively clear water sources, even in drought stricken California. I have filters from Sawyer and Katadyn, and I can't speak for the Camelback UV purifier as I've never used it, but the SteriPen is my usual choice, especially in the Sierras where the water is some of the most refreshing in the world IMO, and the SteriPen is the only water treatment method (except maybe now the CamelBack) that doesn't affect the taste of the water. There are times when I use a filter, but I prefer the SteriPen in most cases.
I had several friends take SteriPens to Haiti for relief work right after the earthquake when Cholera and other water-borne diseases were running rampant. They drank the water (UV treated) there for 2 weeks without issue.
The area that where I agree with the guy is that UV purifiers are electronic devices and are subject to the problems that can accompany electronic devices in the wilderness. In the Sierras, complete failure of the device is not as much of an issue as I only started treating water there a few years back and have never been sick from it, but I always carry a few individually wrapped tablets as back up, and can boil water also if needed. But you do have to take into account the charging or replacing of batteries as well, depending on how much water you need. Again, SteriPens are not perfect.
Boiling water is fine when car camping or if only going short distances and fires are allowed, but is impractical for most people to rely on when hiking more than a few miles. You would have to consider how much stove fuel it would take, or build a fire (not allowed out here) at every water stop. Also, depending on the size of your cook pot, one boil may not be enough to get you to the next water source and you may need to do several boils. Boiling water is still an option, but with the treatment options available today, it usually isn't necessary or practical for most backpackers.