"If you're fighting for your living, its not a luxury most of us can have. Sadly, this often justifies hostility, but I think there's a sane middle-ground here, but curt statements like "be kind" just seems so classist and off-putting to me."

I've consistently found that (in particular when treated with kindness and respect) poorer people respond with kindness in much greater measure than wealthy people. Like the author said, kindness isn't the same as niceness.