We don't have a free market and there never has been one: corruption and nepotism is the source of all great wealth in any capitalist society. Whether we should have one at all is a different debate.
Earning money is not the problem. Most of us have had (or still have) morally-questionable jobs to put food on the table. That's a reasonable trade-off until we have a better, more ethical society. But making it a moral argument to work for the most evil corporations on earth to do good just doesn't make sense. At which point do you become the bad guy you're trying to avoid being through effective altruism?
Earning money is not the problem. Most of us have had (or still have) morally-questionable jobs to put food on the table. That's a reasonable trade-off until we have a better, more ethical society. But making it a moral argument to work for the most evil corporations on earth to do good just doesn't make sense. At which point do you become the bad guy you're trying to avoid being through effective altruism?