Went to DCA yesterday. Saw a guest littering and a custodial asked them to not litter and that a trash can was near the guest....?

I feel he had the right to punch the litterbug in the face.

Everyone has that right. If I saw you littering, I'd ask you not to litter and point out the trash can too.

Of course they did.

Damned RIGHT he/she did!  I would call out and publicly humiliate anyone I saw littering!  When my son was a kid, he threw a cup out of the car window.  I U-turned that car and went back and made him not only pick up the cup, but also every piece of trash that was in the roadside area.  He never did it again!

He didn't tell him not to litter.  He asked him to please not litter.  There is a difference.  It was a request, not a command.

Custodial answer to property management.

Visitors should address managers and not  hired help.   I've seen so-called 'bouncers'

stop sweeping-up trash to drag outside the rude talking trash. 

Everyone has that right. If I saw you littering, I'd ask you not to litter and point out the trash can too.

Of course he had the right.  Guests should follow the rules and be considerate.

Of course. I would much rather have the cleaner tell me to pick my garbage up than get a fine for littering.

Yes, he did have that right. Nobody wants to clean after a disgusting slob.