Yeah, this is an interesting one. I would argue that it's not inherently evil to represent a firm that does some evil, any more than it's inherently evil to work at Facebook, but with a massive caveat. The lawyers LW is describing sound like a more than just firms that do evil as a side effect of their other work, and the lawyers that represent the big climate villains (such as Chevron's lawyers in their prosecution of Steven Donziger) are a hell of a lot worse than cogs in a capitalist machine.

I'd ask LW an important question, which is, does LW think it's more likely that they could survive on a public interest salary (or even a non BigLaw job -- if they're good enough for BigLaw, they're good enough for a respectable normal role), or more likely that their own sense of self and moral code could survive at a BigLaw job defending Exxon and the Koch Brothers. Because realistically, either they'll wash out at the firm, or they'll become a person who doesn't think destroying the earth or murdering Berta Cáceres is all that bad, actually.