Another issue that I see often is when kids use unkind words when they don't agree with what their counterpart is saying - this is especially true when two children are chatting with one another.
For instance, two kids were talking and one said that Star Wars was the best movie ever. The other said, "No, Stupid, the best movie is not dumb Star Wars. It's Avengers..."
I'd like to think that adults would be more respectful to one another when they disagree, especially about such a subjective declaration. We need to teach our children how to be kind, and still get across their own point.
In the example above, it might be very helpful to pull aside child #2, and say, "(Child #2), (Child #1) thinks Star Wars is the best movie ever. That is her opinion. You do not have to agree with her, but you do have to be respectful and kind. Instead of calling her 'dumb' and 'stupid', try saying, 'I don't care for Star Wars. I really like Avengers the best.'"
It may feel a little forced at first, but it's worth pulling your child aside to teach him or her how to converse, and even disagree, with someone in a nice and tolerant tone.
If we don't teach these sorts of things to our kids, how will they learn them?