That doesn't sound like a problem with scooters on the sidewalk, but with riders not being courteous - and the appropriate fix is for people to take appropriate care, not to boot scooters onto the road.
It doesn't surprise me that there are teething issues. Scooters are new and most people haven't learnt how to ride one without making other people feel uncomfortable. That will change in time.
On the other hand, cars have been around for quite a long time and a significant amount of licensed drivers have also been unable to learn how to drive without making other people feel uncomfortable. Betting that we could somehow fix these problems by urging people to be courteous when we haven't yet gotten road-users in general to even respect the law seems like a stretch.
It doesn't seem like a stretch to me. We already have bikes on our footpaths where I live (NZ) and it's a non issue. Cyclists just slow down around pedestrians. People are clearly capable of sharing footpaths courteously. Maybe where you live people are just arseholes, but that's not the fault of the scooter they're riding on.
Where I live, bicyclists should by law be either on the road or on a bicycle path or one of a few designated shared bicycle/footpaths. There are really too many pedestrians for it to make sense to use the sidewalk for bicycles inside the cities, and of course the benefits of commuting by bicycle disappears when you have to move at the same pace as pedestrians.
Also, from my experience with traffic in general, it doesn't take many assholes to make a situation uncomfortable, nor does it take an asshole to be inconsiderate. If one in ten road users or pedestrians I meet every day has a sudden lapse in judgement, that's enough for it to feel uncomfortable.
Actually, that's exactly what I do whenever I'm behind a walker and don't have space to pass.
I'm aware not everybody on a scooter behaves like that, but things will improve as time goes on. You are allowed to tell people when they are riding irresponsibly. They might do things differently the next day.
It doesn't surprise me that there are teething issues. Scooters are new and most people haven't learnt how to ride one without making other people feel uncomfortable. That will change in time.