If there actually was a credible alternative, that would be one thing. But what is it? Start-ups? Yeah right. Non-profits. Please. Government? Medicine? Law? Commerce? Entertainment? Education? Research? Who considers any of these ethical? Some fields may have generally nicer people within them, but the people on top (executives, university or hospital administrators, corporate attorneys, investors, whatever) are generally paid way beyond the value they add through capital or labor, and implement many policies or pursue regulatory capture or whatever else to ensure this type of arrangement persists to their benefit.
The only thing that makes sense to me is that it's a problem of mate selection. If by agreeing to work in a certain field you are tainted with a social stigma that prevents you from attracting the type of mate you want, that might motivate you to use some kind of ethics argument as a rationalization for the true behind-the-scenes status argument.
But I have a hard time believing this matters to finance. Money still tends to be a huge factor in mate selection, ethics be damned. Maybe it matters if you're very low-level in a huge bureaucratic bank, so you get all of the social stigma downside but not a lot of the financial upside. But apart from that... I don't see it. No other choice available to you is significantly "more ethical" than just personally being honest and working in a financial corporation whose higher-level scamminess you can't influence or control.
I mean, it's certainly depressing that it's like this... but this is just how it is.