How we change what others think, feel, believe and do
Grab the moral high ground. When they suggest something even slightly immoral, point out how terrible they are for suggesting such a thing. Say that you would never do such a thing.
Morals and values include not harming others, not being selfish, and so on. Most things can be shoe-horned into one of these general categories.
So, you will forgive me if I take you to an restaurant. Isn't that emotional blackmail?
How dare you ask me to leave the kids alone all night.
Are you suggesting that I should sign the contract just because you took me out to dinner?
Morals define right and wrong. Talking about what is moral, thus is talking about what is right and wrong.
Taking the moral high ground is to become almost unchallengeable. If you are morally higher than others, then you not only are right, but you can even define what is right. This does not necessarily mean you can call black white, but you can take something that the other person has said or done and classify it under existing categories of morality, such as unkindness or selfishness.
When you take the high ground, it puts the other person into a moral double bind: if they argue against you, then they do not recognize what is moral. If they do as you say, then they are admitting to being immoral.
Using morality allows you to attack the other person, which itself may well be an immoral act. However, as you are positioning yourself as morally higher than them, it is difficult for them to take even higher moral ground (which you can respond to by suggesting they are changing the subject).