I'm not for shaming fat people, but you lolitas have to understand that lolita fashion, like any other clothing fashion, looks best when worn by people who have beautiful, thin bodies. If you are overweight and you are truly interested in being the best looking lolita you can be, you need to spend more time focusing on losing weight and less time trying to find creative ways to hide it.
Attempting to defend these women by claiming that people have "different tastes" is a lackluster argument as few people in any society, outside of fetishists, think fat ever looks good. Fat people are shamed because allowing yourself to be fat is a shameful thing. It is an affliction that stems from sloth and weakness. It should never be accepted or celebrated.