Last time that I delved into this topic, I tried to establish that you will be much happier if you don't take offense too easily. This time we will flip that coin over.
If you want to be happy, you should try not to give offense to others. I am not saying that you should be all PC all the time, but you should treat others with a certain modicum of respect. Don't use offensive language, don't use racial epithets, don't use ethnic slurs. Do speak your mind honestly, but defend your thoughts with at least a little bit of logic and try not to belittle people who are attempting the same.
How does treating others respectfully make you happier? It helps you to avoid conflict, and assists in your relations with others. It makes life a lot easier to navigate if you don't go out of your way to find trouble, and you will find that others are a lot more likely to be helpful if you treat them nicely, and God knows that we all have times when we can use all the help we can get.
A couple of caveats here. Respect means treating other people as they should be treated, which doesn't necessarily mean how they want to be treated. As an old platoon sergeant used to be fond of saying, (paraphrased to avoid vulgar language) If a guy is an excrement bucket, I'm gonna treat him like an excrement bucket. Some people are deserving of derision and contempt, but these people are much better left ignored if possible.
Yes, people, the Golden Rule is a good starting point on the road to happiness.