Ethics are all relative, so let's get that out of the way first.
Like any other industry, there are people that are more ethical and there are those that are less. But as long as someone is not breaking the law, you can't expect them not to push the envelope in any business. How ethical is McDonalds for selling heart attacks $5 at a time? How ethical is Google, for taking affiliates money to promote rebills? How ethical was the banking industry for uh, just about everything they do? How ethical are the traders on Wall Street that short sell companies out of existence for a profit?
This shit is business, if you want an ethical career become a nurse or teacher. You can't expect affiliates to play nice while the rest of the business world gets rich. I'm not saying you have to be unethical, but don't fool yourlself into thinking that affiliate marketing is any different than any other business with large sums of money involved.