We sometimes stage. I know units that will go into shootings and stabbings before PD get there, as well as hear stories of crews who would be on the scene and leaving the scene with the shooting/stabbing victim as PD was pulling up.
me personally? If I get a report of a violent EDP, or an armed EDP with no PD on scene, I'm gonna stage until PD get there. stabbing and shootings, I'm probably going to wait until PD get there.
as for staging due to angry callers or foul language, ehhh, judgement call. I'd rather send 2 LEOs into an intense scene followed by the EMS personnel, because the LEOs can make sure everyone behaves, and take appropriate action in case they don't. I've been told by callers "just send the :censored::censored::censored::censored:ing ambulance, and stop asking me why" which usually gets an LEO response because I don't want anyone messing with my EMS crews as they are trying to do their job.
side note, situational awareness is a lost skill. knowing when not to get too far into a scene, knowing how to get out, knowing when to get out, are often forgotten traits. for example, I was dispatched to an armed suicidal juvie EDP running through the woods. Cops are chasing him, dispatch request we stage. my partner stays in the truck, I decide to wander up to see what is going on. a slow walk, I meet up with one of the cops, get a size up the situation, and when 5 cops dog pile on the kid to disarm him and take him into custody, all I'm doing is holding the flashlight so they can see what they are doing (since it was 2am). not getting directly involved, but being close enough to be aware of what is going on in case something goes wrong.
and I would never ever stage for a full arrest, unless there was a really good reason. sooner CPR/Defib is initiated the better the chance of survival.