It's also not certain that obesity is self-inflicted 100% of the time. Google 'obesity microbiome' and you will find research showing particular gut flora which triggers obesity in mice. Consider that e.g. gut flora are often transferred from mother to child, and that in general the bacteria in your gut have to come from somewhere.

Regardless, there's no reason to deny an avenue of assistance to an obese person who wants to lose weight. Simply asserting that they need to stop eating so much is very similar to asserting that an an addict (which is what this actually is, IMO) should just consume less. It usually doesn't work, we know it usually doesn't work, and continuing to just assert that it's that simple is, at best, ignorant.