Maybe not assholes, but it is a pretty blatant status play. By denigrating someone else’s work you raise yourself up by comparison. And while a lot of our psychological health is tied to our relative status in society, that doesn’t make it healthy behavior.

Edit: it's also telling from a status standpoint that you characterized the blue collar comment as "insulting upwards." It would probably go a long way to avoiding those types of comments in the first place if people didn't implicitly think blue collar work is "below" white collar work.