People's perceptions can be momentarily warped so they say something and don't even realize how it could sound to the other person. And, if you don't call them on it, they're never going to know so aren't going to be able to be on the look out for it. That's what boundaries are for, to let people know where they are in relation to you and how you perceive what they say. We all get wrapped up in ourselves sometimes and what we're saying isn't really about the other person but ourselves. If I'm a slob and see another slob :-) I'm not necessarily going to be glad to meet a fellow slob, I'm going to work to not identify with that characteristic and put it all on you. Militarily, think of drill sergeants and how they want to be perfect so find the tiniest things wrong with their recruits? Those most insecure in themselves are the worst offenders.

Speak up if someone crosses the line and says something ugly to you. If it is a boss, do you want to work for someone who like that and does not want to work to be a better person by hearing what you have to say? If you fume inside, that's not being respectful of yourself and you should always be #1 in your life! If you knock your own self down by not allowing yourself to set boundaries with others as to what you will tolerate or not, you will probably end up depressed at some point.