I guess back to the question(s) at hand..........
I have never read anywhere, in any rule book where you can eject a "person" for striking at another "person" on the same team. So, even if this slap happened on the mound, I can't find a rule that says "eject the slapper".
Now, if I witnessed a coach slap a player who is a minor, I will be looking for ANY reason after that you eject that coach. Really. There is NO reason to slap a player, ESPECIALLY a 12 year old!!! The coach could have benched the kid, but he certainly didn't need to slap him! So, while I can't per se do anything about the slap incident, I can make sure this coach doesn't argue another ball/stike/safe/out call without having an early out!
I REALLY hate ostrich umpires when it comes to dugout behavior.
I do not go for sniping from the dugout, and profanity that I can hear on the field from the dugout can usually be heard in the stands, which means it is something I SHOULD be dealing with. All the rule books I umpired under this year specifically say to deal with profanity that can be heard in the stands, EVEN in minor league baseball!
So, the kid yelling out the f-bomb is something I should be doing something about IF I hear it. I may not eject that first time, but there is going to be a warning that EVERYBODY can hear and you will find me staring at their bench after close calls after this warning. Yup, I AM looking for trouble over there, and THAT IS MY JOB!
I don't really want to hijack this thread and turn it into a bench sniping thread, because I believe there are other well-discussed bench sniping threads, but, umpires overall at the amature level should be working to make sure bench sniping does not continue once it starts. I have worked college games with guys that just ignore it, and that really irks me! Almost always, after warning a bench about conduct, somebody from that same team thanks me for doing so. This tells me that many players/coaches don't like bench sniping either, and appreciates an umpire with the balls to deal with it.