I actually completely agree, even as a sanders supporter, there would be a MASSIVE influx of degrees, more education for all, but likely fewer jobs filled. I have a few counter points to this argument however, and I hope you'll listen.
A more educated society commits less crime, therefore the amount of taxes going to prisons goes down. My work colleague is completely on your side, she doesn't want to pay higher taxes so people will have useless degrees, but my counter-point is, "well...look at what you're paying for now". In California alone since 1985 we've built something like 20 state prisons and 1 College. That's our money. Really we have a choice, we just haven't made it, do we want to continue our trend of 3 Million people on prison welfare, or do we want to have a more educated society that commits fewer crimes?
Job Flood? On the contrary, the entire market is changing right now whether we like it or not, more and more automation will take our jobs, so free college or no, the market is already beginning to flood. And, this is the frightening part, low income earners and minimum wage workers, their jobs are going down first. What will they do? And if they're uneducated, does that mean they're more likely to get with the wrong crowd and commit a crime? Doesn't that mean more money to prisons/police? And doesn't that mean more money out of your pocket book to fund prison welfare? It stinks because, realistically, these people don't have a safety net, and they just end up taking our money anyway, wouldn't it have been more affordable to find a way for them to succeed rather than a way to punish them for their circumstance?
We are living in a dangerous time, no candidate is too keen to talk about the changing economy as technology no only makes our lives easier but has the ability to take someones lively-hood away. Ultimately, maybe 80 Billion a year towards free College for all isn't the ultimate "solve all our problems" answer, but I certainly see the benefit to funding education in showing value of education rather than other things, like the 74 billion we pay a year toward prison.