I don't care how you feel about obese people, this type of thing is unacceptable. I don't care what justification you use (race, sexual orientation, dress style, hair color, etc) it is unacceptable across the board. You don't have to be fat to see that this is wrong, you just need to have basic empathy.
PS - I've spent a LOT less time on Reddit as a direct result of how toxic the community has become. Hopefully this will roll that back if just temporarily.