It doesn't make sense to adopt a policy where a person sharing information about what it is like to interact with them must never affect how likely you are to interact with them. If someone tells me they've taken up smoking, they have contracted tuberculosis, they have decided that punching people in the arm is affectionate behavior, etc., then it's kind of them to warn me and they could achieve short-term gains by deceiving me instead until I inevitably notice, but I will not reward the kindness of the warning with my company. The case of lying recurses here where the other examples don't, but my goal is not, "make sure that people who have a tendency to lie don't lie about having that tendency". It's "don't hang out with people who are going to lie to me, like, at all".