It’s a good rule. The tricky part can be distinguishing between what's YOUR business and what’s NOT.
There are two questions I always ask myself before I say or do anything:
"Is it going to HELP or is it going to HURT?"
If it's not gonna help anyone, and it just might hurt someone...then I don't "go there".
If it’s not going to do either, then likewise, I don't do/say it.
Obviously... if it wouldn't help, and ONLY has the potential to hurt....Same thing.
I find this helps me examine my motives, and is a good guide, for when action is called for, or when I need to just MMOB.
JSM