I too think that context for "grumpiness" is important. People who are alone, without accepting families, are not allowed to be grouchy to others they interact with. In a work situation, being excessively negative is not ok, especially for the boss. People who are around/work with children, or those who are ill or struggling need to find another way/place to be grumpy. I agree that being human means we all have a range of emotions that are real and valid, but it's also true that there are consequences to grumping on other people - for the grumpee and the grumpered-at.