Sometimes it's funny to see a Sim being slapped by 50 (ex-)lovers, but other times it makes me feel uneasy. Is there a hack somewhere that just makes them yell at the other Sim instead?

I'll try to help, especially as you answered my WCIF so promptly.

I can't think of anything that exactly meets you requirements. The nearest I can think of is Squinge's no autonomous bad socials collection, but I fear it does rather more than you want:
This mod prevents all Sims from autonomously doing the interactions listed below:
Fight - Attack, Slap, Poke, Shove, Argue
Irritate - Insult, Annoy
EP3 is required to use this mod.
miriamnz recommended it to me a few years ago in a WCIF I started looking for mods to reduce violence. You might find that thread interesting. I didn't install that mod then (partly because I didn't actually have EP3 (OFB) (although I did have the OFB game engine -- it came with Double Deluxe). I've just installed the mod now to try it out. It seems to be working ok.

Another hack that reduces violence a bit is Chris Hatch's Men don't hit Girls from BAS (which for some reason I can't log on to at the moment, so I can't give you a link, but Charity mentions it in her thread on family-friendly BAS items). I've had it for a few years now. Personally I find male on female violence particularly unacceptable (I've never forgiven Mercutio for hitting Hermia in the very first scripted event I saw, and neither has Hermia!). It seems to stop males slapping females, but I think still lets them poke them, which I always think looks more painful and I fear carries a risk of an eye injury.

A mod to civilise the game by stopping really nice Sims from resorting to violence unless provoked beyond all endurance is on my list of things that I just might try to do one day. (First I'll have to learn how to write mods!)

Sorry to be so slow -- I've had this reply half-written for a week.

Thank you AndrewGloria, this one by Squinge is perfect for me. Oh how I hate these behaviors.

I thought I responded to this already. Sorry for taking so long!

But thank you. I'll check both of them out and see how they work in my game.

I like to use this no-jealousy hack from Smonaff for my romance sims working up large numbers of simultaneous lovers. Without it, it's impossible to go on a date at a community lot, without another lover showing up and spoiling the date score.

For that purpose I usually just rely on Pescado's Romance Mod, which stops Romance Sims getting jealous if their Outgoing, Playful and Nice points add up to 15 or more. This also applies to Pleasure Sims, but they still get jealous if they're married, engaged or going steady. This has the advantage over Smonaff's mod that I can have married couples invite a "friend" over, and both have woohoo with him/her! In New Desconia, the founders' bedroom has two double beds! In addition the Sim Manipulator allows me to turn individual Sims' jealousy off or on. I recently used this feature to include a Popularity Sim in such an open relationship. Presumably the Sim Manipulator loads after the Romance Mod.