I agree that the boundary part is critical. It's a question of timing. When someone is acting that way, they are not open to hearing it. Also, "disrespectful tone" is not an objective fact but a judgment - and a criticism. No matter how "true" it may be, it will likely be heard as such, and will only decrease the chances of the limit being heard.
If the objective is to set a boundary, then doing it at that moment is not effective. Doing it after they are validated is.
