"IF WE ARE nice to them, they will be nice to us." This is the assumption behind the basic human principle of reciprocity, one of the foundational cornerstones of almost all cultures. If you cooperate with me, it almost compels me to cooperate with you. This is a sound principle of human relations, used to good effect in business and all other spheres of human interaction.
But reciprocity isn't inborn. It is taught. Reciprocity is intentionally and painstakingly hammered into the heads of our children until it is instinctive.
But unless you're very young, you have found out, probably painfully, that some people do not follow this principle. There are a small percentage of people who will accept your generosity and cooperation and do nothing for you in return, and have no feeling of guilt about it. They do not reciprocate. They are either sociopaths, or they never had this basic principle pounded into them at an early age.
Once you recognize someone like this, how do you treat such people? Do you keep being nice? Do you keep giving? Do you allow them to continue to take advantage of you? Maybe for awhile, but eventually, what will you do? You will stop giving. You will stop being nice.
I'm sure you have figured out why I'm bringing this up. Some ideologies are not reciprocal. Islam is one of those. It divides the world sharply into us and them. In Islamic ideology, reciprocity between Muslims is instilled. But reciprocity is sharply discouraged with non-Muslims.
Islam is a ratchet. It only goes one way.
Just as there are some people in this world who will only take advantage of your kindness and generosity, and will not reciprocate, there are some ideologies that only take advantage of fairness and accommodation, and will not reciprocate.
What shall we do with the people following such an ideology? What's the appropriate, sane, intelligent response? Tit for tat. That is, you begin with cooperation, but at the first sign of a deliberate lack of cooperation, you cut your losses and respond to a lack of goodwill with an equal lack of goodwill.
It is foolish, self-defeating, and counterproductive to do otherwise. Niceness doesn't work with everybody.