I don't really think the arguement is about just pointing the finger at people who are obese,but rather people who are obese and then blaming others for their condition.
Using your hair dyeing comparison,people choose to dye their hair,but they dont blame people because their hair is dyed,they did it themselves.
I think its okay to be obese as long as the person understands the health risks involved,but its really not okay to blame someone else,such as a fast food train like McDonalds, as if they brought this upon you in some secretive spiteful way.