Teach children to speak in respectful and loving tones of voice no matter what the situation.
I know that my children get cranky and next thing I know one is using a snippy tone of voice to another. In our home, this is absolutely not allowed. Usually, all I need to do is to stop the conversation and tell the offending child to try again with a kind tone of voice. Just because they are bothered they don’t have the right to speak unkindly.
A sibling is much more likely to cease an annoying behavior when asked kindly to stop; whereas when one child says, “STOP THAT!” to another, that sibling tends to engage in argument, or purposeful annoyance just because of the mean voice used to make the request. A calm voice can stop a bad situation before it even starts!