I like your <type> statement because it draws to the bigger problems with generalizations. It's also the weird logic flow I see more and more in western culture.
"Privilege" is a word I hear thrown around a lot today. Often times when people use that word, they do not realize they are making broad assumptions about other peoples' circumstances (typically) based on an ascribed attribute.
To go even further in relation to this and air travel, is obesity ascribed or achieved? If you get charged extra for being tall, that's not something really in your control. Discriminating against an ascribed trait isn't really fair and is the reason for civil rights legislation.
There are cases where it's difficult to determine if something is ascribed vs achieved. This is why laws for marriage equality have taken as long as they have in much of the world.
In terms of obesity, we see the trends and we see it's increasing. This is something we can measure. Homosexuality was something that could be hidden, and therefore the measurements could easily be off as people may have lied in previous decades to fit in with social norms.
Ultimately, fighting obesity has a lot to do with education, and changing some of the very wrong ideas we have about what is and isn't healthy food. But that's another matter.
In the article, they're mostly describing airlines that weigh people to distribute loads on planes. That seems logical. Now in regards to airlines charging them a different price due to weight and fuel consumption, that gets into a very grey area of how we deal with the reasoning behind obesity, choice, human rights and market costs.