The last claim is predicated on the idea that many low-wage/fast food jobs are held by teenagers who, biologically/neurologically are not wired to consider longer-term consequences. I'll find a cite if needed.
So, I'd ask, how responsible is BK for developing a business model that puts low-wage workers front and center as their primary point of production and primary point of contact with consumers?
Lastly, if BK did bring suit, what do you think they'd be able to recover? At best, garnishing minimum wages – if the person had better financial reserves or means, they'd likely not be working production at BK.