I think it’s just most local governments don’t wanna divert city funds towards making things like side walks or bike lanes. But they also don’t put legislation in place that mandates incorporation of such things when building property. Some people may be against it since it would increase their property taxes by increasing property value.
There’s no problem with fatphobia in my opinion. I don’t like people who don’t take care of themselves. “Well if they could be skinny they would be.” Well, if you think that walkable cities are a dogwhistle for fatphobia, you are ADMITTING that fatness can be fixed with exercise (and a calorie deficit). While there are medical conditions that make it harder to lose fat, it is very doable.