Let me strengthen my position by adding that it is also moral and ethical to seek a return by investing, providing you make reasonably ethical investments. Maybe not in the coal industry or whale meat industry - but any number of things can be perfectly ethical and even beneficial to society at large.
It is not immoral or unethical for somebody to have or earn more money than another. All people try to increase their wealth however they can. At lower income levels that is very difficult but the behavior is the same.
"All wealth levels" are not the same.