It's easy enough to know how to "handle" someone who is inappropriate at times or that you are not 'entangled' with in relationship or work. But, "handling" someone who is inappropriate in continual, dysfunctional ways that you have to work with or relationship with is not always as obviously easy. I'm not talking bad jokes and foul language inappropriate because..well come on, that's my thing ;-) I'm talking about abuse of relationship inappropriate.
Case in point, a client that is continually berating you in a passive aggressive manner, in and out of the presence of other clients, can seem impossible to "handle". Here's why: Aggressively talking back at them does not work because they are being passive aggressive for a reason. They don't want to confront the real issues, and certainly aren't going to own them, so 'calling them out' is only going to get ugly, make the other clients feel awkward, and probably cost you a client or two. Playing their dysfunctional, passive aggressive game doesn't work either. They delight in getting to feel heard without being accountable, so this little duologue serves no real purpose, and is extraordinarily frustrating. Knowing why this person is the way they are, as well as knowing what their real issue is through all the passive aggressive bs is part of then knowing how to contend with their behavior in a functional way. Removing your own feelings of wanting to eviscerate them to avenge yourself is definitely a must. Now, you can practice your functional use of the Four Agreements in this unnecessary situation. Be direct not subtle. Say what you mean with no passive aggressive vagueness. Don't get into a whole allowance of them to continue bad behavior by dragging you into an argument. This shouldn't be an argument or an airing of grievances, but instead a tactful bottom-line of what will not be deemed acceptable in this relationship (a.k.a., your boundaries). Since you have arrived at them being passive aggressive for the reasons you did, and knowing that an argument with them is futile...also knowing that you cannot control another person (reaction, feelings, behavior, etc.), then your approach of tact and boundaries of the main issue is all you can do. Their reaction is probably to pout and tantrum, which is a whole other thing, but the same holds true in that actions equal consequences. Their actions may be the consequence to both of you of them having to leave your establishment, so before entering such a line in the sand you have to be willing from a business standpoint to pay that consequence for someone else's bad behavior.
The same strategies used above applies in all personal relationships, just with the absence of it being a business transaction, etc. Being true to your word, and in all things saying what you mean without pretense, vagueness, or passive aggressive nonsense. Owning your part in action and feelings. Setting your boundaries without being harmful. Harmful is different than being 'hurtful'. Since you cannot possibly control another's reaction or feelings, then you cannot possible be direct and tactful without some hurt involved. Being harmful is to be intentionally mean....saying more than is necessary to getting your point made or boundaries set. In resolution to any issue in relationship there is no need to draw blood.