Boycotting things that are produced unethically is completely impossible in a capitalist society. Doing so is mostly an adorable waste of time that serves more to make the boycotter feel better about themselves, and superior to others. It does absolutely nothing to deal with the root sources of any problem.
It is not impossible to boycott unethically produced things. You can always buy fair trade sugar over unethically produced sugar. You can always stop buying something entirely if there is no ethical way to produce it(such as with meat).
Of course boycotting doesn’t deal with the root source of the problem, but you’re also not personally giving your financial support to the problem. This nihilistic type of attitude does far less to change anything than boycotting ever does.
Or, put simply,
"I can’t change EVERYTHING so I choose to do nothing. Capitalist societies are inherently unethical, so I should try to make myself as much of a tool for capitalist society as possible. The path that is easiest and most supports mainstream capitalism is clearly the most anti-capitalist."