This is not black and white. Often we are optimist and we ignore the suffering of the ones closest to us because we simply don't believe they are suffering.
That doesn't have anything to do with being optimistic, as far as I can tell. Dismissing others' suffering is caused by a lack of empathy or by selfishness--the two go hand in hand. It can certainly seem to a depressed person that an optimistic one is oblivious to their suffering, but it is not always the case. I think the best you can do with negative people is make it absolutely clear that you acknowledge their pain while getting them to progressively come out of it.
If another person's internal mental state isn't visible, so we have to work it out from things that are visible, there might be a wide range of possible guesses and so being optimistic or pessimistic might produce very different results.
Has my friend Joe stopped coming out with us because he's busy with a great new girlfriend he just hasn't told us about yet - or because depression means he can barely get out of bed in the morning let alone leave the house?
