> This is such a common argument, I'm sure it has a name.
Someone who is willing to do the unethical dirty jobs that take a toll on society, because they pay so well and because if he didn't take them, they'll just hire someone else to get it done?
Yes, the name for that is "mercenary".
Adjective: Motivated by private gain.
Noun: A mercenary is a person primarily concerned with making money at the expense of ethics, [most often used to refer to a soldier who fights for hire].
Interestingly, being "fun and intellectually challenging" doesn't really factor into pattern much, except as a justification certain people need to make the job seem more glamorous or honourable. But as it happens, even with that factor absent, if they don't take it, somebody else will, right? For the right price, of course. The difference between those prices is literally the monetary value of your honour. Most people won't set a price on that, but you're a mercenary now, so you already did. Funny thing is that difference isn't exactly traded on a free market, it could even be negative, however/whatever gets the job done for your employers.