People act in accordance with their notion of identity. There was a study about voting that showed that getting people to identify themselves as a voter resulted in statistically significant increase in them actually voting than asking them if they would vote or having them pledge to vote.

For this reason I take issue with replacing “we don’t talk like that” with “please use kind words”

The former helps form the child’s identity as a person with values, one of which, is not using mean words. The latter is a plea to abide by the parent’s values.

It is not cruel to raise your child to have values and to instill those values. I would argue it is cruel to deprive a child of those core values and replace it with some sort of obedience to authority which is what the updated phrase instills.

Ima try some of these with my parents. Might help