I'm probably totally off base, but the only scenario that makes sense to me is that the sheriffs were on the look out for suspects in some kind of fairly serious crime. If the Uber vehicle matched a description and was pulled over to check it out then the stern approach until the officer knew it wasn't the car/suspects they were looking for makes sense. The only federal interplay I can think of would be some kind of terrorist threat, maybe some kind of trafficking, pornography, or a gun type crime. Without hearing a tape of what was actually said it's hard to say. Wonder if OC has body cams on their officers or patrol cars.
The warning to not come back may have been good advice. If the OP's Uber car matched the description of what the officers were looking for or if there was some kind of heightened alert due to a threat so that everyone was being scrutinized OP wouldn't want to get pulled over again!
Unfortunately in the world we live in any of us can end up in the wrong place at the wrong time. IME, when you are pulled over, even if you don't know why, the best approach is to be polite, listen, follow instructions and answer questions. For a regular law abiding citizen that's not easy to do and it's a bit scary to get pulled over, but staying calm is best. Don't ask, don't volunteer, don't interfere. If you don't know why you're pulled over, assume there's something going on and that the officers probably won't tell you about it. They'll tell you if you were pulled over for speeding, but they won't if they are looking for some dangerous person still on the loose. The worst thing to do is to argue about why you are pulled over or to over react - you prolong your encounter and you slow the officers from finding the real threat if there is one. It is quite traumatizing for a law abiding citizen to be inadvertently caught up in a scenario where there's an active hunt for a dangerous suspect, but at least this wasn't a felony out of the car at gun point stop & frisk.
Not saying this is what happened here necessarily and I find the golf carts to be odd - I've seen oodles of OC sheriff's cars all over property when there are heightened threats. Not sure about the call for back up, except maybe the crying & all created issues in the officer's mind. Anyway, it's one alternative scenario as opposed to an out of line cop scenario or a person impersonating a cop situation.