Aren't there two separate things under discussion here?
First, things you feel are morally repulsive, and won't do at any price,
and
Second, things you think are tacky or would diminish your reputation, but will do for the money because you can do them better than anyone else; because if you don't do them. someone else will; and because the money is welcome...
The borderline between 'tacky' and 'morally repulsive' is, I freely admit (after more than a quarter century in journalism) ill-defined and can be influenced by the size of the cheque (check for American readers); but for me it's a fairly narrow band, and I'll write rubbish (under a pseudonym) if I don't actually find the subject matter against my principles. Thus I wrote 'Comet Catastrophe' (about Halley's Comet) as Roger Sutherland for a few thousand, but I'd never try to to make a serious defence of China's behaviour in Tibet.
Cheers,
Roger