That web site is run by the PCRM (physicians committee for responsible medicine), which is not run by physicians at all as far as I have ever seen. They are an animal rights / pro-vegan group who are against Atkins-like diets because of what they view as excessive animal product consumption.

When I was thinking about starting Atkins, I read through a lot of what they had to say, then looked up their studies, as well as doing searches on PubMed (the online database of virtually all scientific publications) for low-carb diet studies, and found that they had little to no support other than anecdotal for their claims.

I recommend reading some of the real medical studies done on Atkins diets, which you can even search for on Google, and then discussing the real results they found with your boyfriend. In a nutshell, the biggest "negative" is that in most studies done, the people who stuck to the low fat/cal diet lost equal amounts in comparison with the low carb diet. The biggest positive is that the low carb people were more likely to stick to the diet, and their blood work looked better. I think the "negative" is a good thing because I know that many people do lose weight on low-fat/low-cal, so I would have been suspicious of a study that found that those people didn't. The fact that low-carb works AS WELL to me, but that more people, including myself anecdotally, are able to stick to it, makes it better. Or at least as good, which is really all that matters for a diet since YMMV on any diet plan.