Who's fault is it that they have to make a career out of fast food? Companies aren't paying for the people, they are paying for the labor that the people produce. The labor produced at a McD's isn't worth $15 and they shouldn't get $15. Have you ever worked fast food? I have and I can tell you that at the most $10 would be acceptable but nothing more. If people can't survive working the fast food industry then they should be improving their skills so they can get a better job.
What do you say to the people who have skills and are making $15 hr for their work? Sorry but your skills are now worth the same amount as someone who flips burgers or drops fries in oil? This demand for a living wage wouldn't be a problem if people took control of their own lives and did something with them instead of expecting others to do it for them. If your over 25 and working at a fast food joint, you really need to look at your life and figure out what you did wrong. If they are a high school drop out then I have no sympathy for them and they deserve fast food wages.
The funny thing is that our society needs fast-food workers, laborers, truck drivers, farmhands, clerks, et al., and similar low-wage occupations. Again, these people should be treated with decency, not looked down upon, and should be paid a good wage.
If skilled people, such as beginning teachers, are being paid $15, they should join a union and demand better pay.
As for your derision of, say, dropouts, some people are not cut out for school. That doesn't give employers the right to pay cooly wages. These people work hard and should get good pay.