Being “good” or “kind” to someone is not attained by just going along with whatever weird or crazy thing they say even if I know it’s wrong, or when I think that they are making a mistake, in some misguided attempt to protect their feelings.
To the contrary, that is being selfish because it suggests I would rather play along with something that I know is false, and may cost them at some point, just so *I* can avoid the stress of having to tell them the truth.
Doing the right, or “good” thing, would be in finding a way to communicate that truth, even at the cost of our comfort.
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Shorter version: If you care about someone, you tell them the truth. If you don’t care about them, or if you want something from them, you tell them what they want to hear.