That reminds me of this saying by...I think, Dale Carnegie..."No one needs a smile more than someone who doesn't have one to give."
I think when we send negative energy to such people they become more negative. If we send positive energy, it helps them to become better. Sometimes we look at people as grumpy but we don't know what troubles they have to deal with - we don't know if anything or anyone has hurt them and made them this way.
We don't lose anything by giving a smile. A smile can go a long way.