If I were like the OP (and I once was) this thread would have left me curled in a ball on the ground, inactive and helpless, especially with all of the debate about companies eating dead people.
But this stuff is actually fun because it's about freedom, and it's only as morally sketchy as you are.
For example, yes, it's possible to deal in scummy P2P loans. It's especially common, in my opinion, when you start getting greedy and chase high returns on stupid loans to nutcases buying $10,000 honeymoons when they can barely afford food.
On the other hand, LendingClub loans start at under 6%, which is half what a bank would charge and a damn good tool for helping people refinance unfair credit card rates. Yes, some people will lie and a few will default, and that's just a cost of business. Most investors still come out far ahead of the pittance most banks will give you. That said, P2P is relatively new in the world and I personally keep only a small percentage of my money there (although enough that I can weather defaults on a few loans; I spread the risk out among lots of people and it becomes manageable).
As another example, index mutual funds are a proven, sensible way to invest. Unfortunately, a simple index will put you in bed with a few companies that do really questionable things.
But there are a several indices that automatically remove or reduce some of the worst offenders for most socially-responsible investors, leaving you with flawed and human, but not horrific sets of companies to own at below average fees. Some 401k plans, like mine, offer good funds that track these social indices. One might miss out on some profits compared to an unscreened index, but many do a reasonable job tracking the overall market. I would avoid the more active green funds, with higher fees, because it does start to eat into retirement and I see no reason to believe an active manager would perform better than an index.
All of that said, I probably would have chosen Betterment a few years ago. Their unscreened indices would have been a bit uncomfortable, but the moral problems do feel worse for me as the amounts invested gets bigger. Realistically, filling up my gas tank once probably does a lot more damage to villagers in Africa than the few dollars invested in Shell when the overall amounts are small. Over time, I'd move the money into investments closer to what I currently have, once I'd had a chance to do some homework.
Cheer up! We're blessed with more, lovelier, more socially conscious options to invest our money in than any of our ancestors, from real estate to solar power, to low cost mutual funds, to local businesses. Spend a little time learning a few things, read a Boglehead book to get started, dip your toes into a small test account, and be awesome.
Because I also detect lots of disillusionment with capitalism, I'd suggest reading up on The Wealth of Nations, which is basically a founding document of our modern society and a lot more optimistic than I had expected for a hundreds-of-years old book on economics. The world does suck, but it's also wonderful. Understanding why our society was built this way makes it easier to do good.
