I don't understand how this is a topic that needs to be asked.. they can wear whatever makes them feel comfortable..
You wouldn't even know the girl's purpose for wearing yoga pants, there could be the chance that the day she chose to wear those pants is the day she wants to change to a more healthier lifestyle.. She might have wanted to exercise in them or do actual yoga or something. If this were to be a reason, and some random person discourages her, than that person could have just ruined this one girl's chance of doing something good for herself.
People can wear whatever the fuck they want. Its their right. That being said, it totally depends on the circumstance and the girl that is wearing them. Overweight is a broad term and everyone's body is different
I never understood why this bothered people, it's the same with people that're bothered by pajama wearers in public: no one is hurting you by wearing clothes in public. This is the epitome of a first world problem: "Oh woe is me, people are wearing clothes I don't like on them!"
Even if you don't like it, it is not exactly illegal or anything, nor should it be. It is already problematic enough that some people legitimately harass and or murder others just based on what clothes they wear.
Im sorry but no one wants to see your cellulitis ass crack or the rolls of fat hanging over the waist band. Before a large woman goes out in these she should look in the mirror and ask herself do hippos wear yoga pants?