Business is business, I see my role as facilitating the needs of my clients. If they ask for something to be done in a sustainable way, then great, if they are open to suggestion on this point then maybe I could offer some advice, but at the end of the day it's their concern because it's their business.
My responsibility extends to how I run my business, not how others runs theirs.
Obviously there might be situations where I would have to question my position depending what is being asked of me, if I find something morally wrong, I will refuse. Luckily I haven't been tested on this point yet.