All value is "out of thin air", or really "in our minds". If the banks want to buy bitcoins, they will do so at a price agreed to by the seller. That's how markets work, the buyer and seller agree on a price.
I'm not sure how exactly "they would run it to the ground", or how they "can destroy Bitcoin at any time".
You don't think the the banks or government can manipulate the markets? Outlawing, extreme taxing, using the media as a tool for propaganda, etc. are just a few ways.
You also don't seem to understand the distinction between money and wealth. To be clear, money is not wealth, it is what you use to purchase wealth.
If Bitcoin is supposed to be money, why is one worth $700? Or anything at all?
The people using bitcoin today are not getting rich for "pretty much next to nothing". Just because you can't see the value in what someone does, does not mean there isn't any.
If I bought
BTC1000 for $1000 a couple of years ago I didn't do much to justify having $700,000, or the ability to suddenly buy a house and fancy car. Excuse me if I don't see much 'value' in what I did. The problem is our notion of what is valuable. Hard work or even smart work isn't valuable-- getting as much as possible for as little as possible is what passes as valuable nowadays and is precisely what gives value to Bitcoin.
And finally, bitcoin is an experiment in libertarian/Austrian money. The goal was not social justice or wealth redistribution or any other left-wing nonsense. If that was what you wanted, go check out the altcoin section of the forums. I'm sure there are plenty of scamcoins there that aim to do what you want.
There was a goal of social justice, just not for everyone-- you know, not having banks or governments controlling and taking our money-- remember that? By saying there wasn't means you are admitting that Bitcoin is nothing more than speculative greed driven 'value' quite literally based on nothing. What other usefulness does it have over classic 'money'?
And because you mentioned all the other altcoins-- wouldn't they make Bitcoin 'tech' seem redundant (if that were another aspect of its 'value')?