It's both, poor pool etiquette and sharking as well. There are rules against things like this.
ANYTIME, I encounter my opponent attempting to hit balls on another table, I immediately tell them in a nice voice, "You can't PRACTICE while you are playing a match!". If they say it isn't in the rules or some other silly thing, I tell them in a loud enough voice for more than just him to hear, "Then you don't know anything about the rules of pool."
That usually dissuades them from attempting to distract me further but if they attempt other or further distractions, I address that as well.
The absolute worst thing you can do when something is distracting you is to try to ignore it. At least that's what the Sports Psychologists have taught me.
Sometimes, you can use the distraction to motivate you to focus even more and that's fine, but it is my belief that a sharking opponent needs to be embarrassed at the very least if he doesn't immediately stop the distracting.
I've embarrassed professional pool players when they didn't act like gentlemen when I asked them to correct their behavior so I don't mind doing the same for league players or anyone else.
The main thing is be resolute with your decision to denounce the distraction and accept nothing less that decent behavior from your opponent. It is imperative that YOU are not embarrassed for calling them out. Any guilt on your part will hamper YOUR ability to play well. I used to be self conscious about calling them out but no more. Life is too short to put up with any shenanigans at the table, intentional or unintentional.
If my opponent is a really nice guy and just doesn't know better, I will be very patient and nice and explain why I don't tolerate that type of behavior (besides it being a rule). If they want proof about it being a rule, I tell them to please go get a ref.
JoeyA
APA bylaw in Vegas: SPORTSMANSHIP: Participating in the APA League is supposed to be fun. Cheering for your team members is recommended and encouraged. However, heckling, jeering, interrupting, distracting, cussing at, or screaming at your opponent (to deliberately cause a disruption), opposing team members, Division Reps, the League Operator or any APA official is a show of poor sportsmanship and will NOT be tolerated.