To use an equally contrived example of my own — there's plenty of jurisdictions where arguing something along the lines of "look at how she was dressed, she was asking for it" will get you off the hook on rape charges. Would you still argue that an attorney who makes that argument is merely "advancing the most effective defense of their clients"? Or would you find that conduct reprehensible both for the attorney, and the client who allowed the attorney to use that line of reasoning?
Ultimately, it's your own choice what lines of arguing you present, and you don't get an ethical freebie just because it's "effective".
Ultimately, it's your own choice what lines of arguing you present, and you don't get an ethical freebie just because it's "effective".