That's often a very complex judgment call. We can empathize with someone's emotional state without necessarily believing their factual claims, however. "You are (or might be) objectively wrong" doesn't automatically imply "therefore your angst/joy/pain/hopes are not real". People can also misrepresent their emotional states, but that's a good candidate for giving people the benefit of the doubt: unless there is clear evidence of dishonesty or confusion, each person is in the best position to know what they themselves feel, so it's one of the few cases where presumed competence is a brilliant approach.