Shows that you think both the person as well as what they're saying is insignificant enough that they can be interrupted and talked over

It's a win-win situation for the interrrupter

Because if the person who's getting interrupted and talked over doesn't call it out then they look weak

But if they do call it out then it makes them look defensive

A good technique I use if the person tries to shut down the interruption is to say something like "Calm down, I'll let you finish what you were saying"...then go on saying what you were when you interrupted them

Basically it keeps the interruption going and it's as if you're giving them permission to speak later on when you're done interrupting

Passive-aggressive power moves like this are what I use to get myself hated by everyone who encounters me

Smugness intensifies.

I just stop talking burt stare them and when they notice hit them with "you done chief?"