Factually you don't, and people have tried being nice to carnist for... oh I don't know 3 thousand years?
If you're stupid enough that you'll only consider doing the right thing if people act sycophantic then I'm going to mock you for it. You absolute dreg, you moron, you shiver looking for a spine to crawl up.
Unless you're just a vegan trying to be nice in which case I respectfully disagree in circlejerk coms as above. You wonderful, shining, humble paragon of virtue and peace.