Even if you think to yourself it's not a big deal and you should "just let it go"

It's actually people subtly testing you to see how much they can mistreat you and get away with it

If you don't call it out and confront them on the spot then over time you develop a reputation as weak and afraid of confrontation

For example if someone interrupts you while you're speaking a lot of people will just let it slide and pick up the conversation when the person who interrupted them has finished speaking

But that was a test

You immediately have to call them out, even insult them a bit in front of everyone, to put that person in their place and send a message to everyone else

Don't disrespect me like this again you little bich or else.