That's why I say it's confounded. If you say "I won't treat fat people (the same) because they are less likely to survive", and then afterward say "Fat people

That's why I say it's confounded. If you say "I won't treat fat people (the same) because they are less likely to survive", and then afterward say "Fat people were less likely to survive (so this earlier decision was justified)", then that's severely faulty and dangerous logic. The reason fat people had worse outcomes is, just as likely, because they had worse treatment.