Think about it: The worst thing you can do when others are making fun of you is to show that such action bothers you. Instead, smiling in the face of insults from a crowd you cannot beat, "agreeing" with hurtful remarks and walking away, is the fast way to shut down a bully's comments. They WANT their action to irritate. Trump did not give Putin that pleasure.
Over the years, we have learned that the Leftouts have no clue how to deal with bullies except to cry and whine and "go tell mommy." Trump (and millions of blue collar types) is great at "giving it back" to the bullies of this world.
Here is what happened:
Putin: I am expelling 755 of your diplomats. That will teach you to mess with me.
Best response: Hey, Putin baby, I was cutting over-staffing, anyway. Thanks
THAT is what happened and if you can't see the humor in this, you do not know how to deal with a bully.