It is like any form of personal transport, it all depends on the driver and just as there are really bad selfish car drivers, some people using mobility scooters are selfish and careless scooter drivers.
The other problem is to do with the size of the scooter. Just as some 4x4 cars are the size of a lorry, need two parking places and are driven by loud arrogant people, who think the world owes their 'car' space to do whatever they want , so there is a category of mobility scooter owners, mainly men, who buy the scooter equivalent of a huge 4x4 - and think that they and their vehicle should have priority at all times and in all places. They block supermarket aisles and drive everyone on the pavement in their way into the road.
How I react to mobility scooters, tends to vary with size. people on small ones appear to me like ordinary pedestrians and i treat them as such, but as the scooter gets bigger, I become more wary, and when I see those huge ones with the kind of bodywork means the owner can pretend he is on a high power motorbike, then i hate them and their arrogant owners, because owners of that kind of huge scooter, is arrogant or they would not have bought such a huge space grabbing vehicle in the first place.