Now, does it improve liquidity? Investopedia claims so, thus, making capital cheaper and making it (in theory) easier e.g. to hire new people.
http://www.investopedia.com/articles/active-trading/050515/l...
In itself it's not evil and actually beneficial. Lower transaction costs and more liquidity means there are more resources to go around. What people actually choose to do with the amassed capital is another thing then entirely.
Does it cure cancer? No. But blaming smart people from not trying to be a superman is stupid. Very, very few alone are that smart that they alone would make a huge difference.
It's hard to see why a career in finance would be less ethical all around than a career in some company that just harvests clicks.
Science currently, as a career choice, needs burning enthusiasm or it will burn people out - I see no reason to chide people for not choosing it.
As a fairly low-income engineer I find it hard to see any other reason than jealousy to bash people in finance in the general context.