That may be a secondary issue, or a red herring, depending on how you wish to treat it. If you wish to treat it as a red herring, you will continue to piss people off like jkurz etc without achieving any debate-related outcome. That's what red herrings do; inflame emotions and distract people without impacting an outcome.
If you wish to treat the similarities as a secondary issue, you must admit that the origins and treatments of cancer are far less well understood then that of obesity. If you remain uncertain, do your research, but I will tell you as a medical publisher who deals often with oncology that the banner of "cancer" encompasses hundreds of conditions, all with their own origins and treatments, whereas the roots of obesity and treatments for it are far better understood.
Even as a secondary issue your points aren;t very strong.