Recently I substitute taught at a local school that was celebrating Bully Prevention and kids kept coming to we and telling me about some minor thing another student had done or said. They were obviously proud to be telling me, and sometimes the other kids they were tattling about would even accompany them, wait to be asked if they had apologized, and say "Sorry." Obviously they weren't actually feeling any guilt.
I went along with the school policy since that's what they were paying me to do, but I have serious doubts about the ultimate success of the program.
All adults sometimes get negative comments from other people and we can't just run to a teacher or other authority figure and tell on whoever said them. In this world kids need to learn to cope with things like that.
Of course if someone is seriously harming or endangering others it may be necessary to report them to authorities. That's why we have police and courts.
And it is worthwhile to teach children that mean comments to or about others aren't polite. But I'm afraid in the long run encouraging them to be tattle-tails will do more harm than good.
A while ago I did a series of posts about bullies and a way to handle them that really works. If you go to the top, left side of this page and enter "Bullies" in the search bar you can see all my previous posts on the topic.