How stupid is Language Bias

In class we were going over certain rules about language bias. I've never liked going over this subject. My opinion has always been that if you want to be offended then go ahead. That has changed a little. I know someone who is a financial advisor. I know him very well and know a lot of the people that he has worked with. Just a couple of days ago my friend and his boss met with someone that I work with. My coworker came back very disappointed by them. My friends’ boss didn't treat him the way he thought he should and almost cost my friend some business. On another occasion I was talking with my friend and his coworker. He said that what I was doing financially was stupid. Something that didn't really bother me because I really don't care what he thinks. But there were other people present that heard the same comment and their outlook on my friends company isn't very good right now. I am realizing that it really doesn't matter what I think. It is very easy to ruin your company’s reputation. It may be something very simple. It doesn't matter. What matters is that it just cost you and your company customers. It is worth going out of your way to not offend anyone for any reason.