I spent 24 years in the military, where quitting is not an option. An excellent way to get the point across that you will not take the blame for your boss's orders is to request written instructions.

Boss: "Do this and do it this way!"

Me: "That way is [ unsafe/illegal/otherwise proscribed ] because [ the reasons ]."

B: "Do it anyway and do it this way."

Me: "I'm not sure I can remember exactly how you want it done. Would you please write down step-by-step directions?"

One boss actually did so. Turns out his bosses were tired of him too...