For an especially clear-cut example, SEO is certainly unethical from the customer's point of view, but I absolutely have to do it, and will.

SEO is not unethical when it focuses on findability. Making your site reachable by the people who are looking for it is not manipulative - it's just good customer service.

If you are doing something unethical, you should reconsider whether you "have to" do it. Hurting your customers is not good business, and you're making yourself an enemy of the people you purport to help.