I agree, the use of charm is to get someone who would/is not ordinarily friendly toward you. A tired no non sense bouncer, an arrogant Lord of the land, an aggressive merc looking for your bounty.
A successful cast of charm changes the way these people see you, and then make them more likely to listen to you. Suggesting harmful actions to themselves or others they deem to be friends or family will not work with a successful CHA check.
As before you can get he chance to convince them of things they would do in the normal/pre-charmed disposition. ie, let you into the theatre, persuade a more favours out of the Lord, Pay off the merc or hire for your own cause.
In my experience as a DM the best use of Charm on a party member was to have go find the other guards to help their "new" friend. The PC was only told they were upstairs, and so spent the entirety of the combat somewhere else upstairs looking for help.