They do sometimes seem a tad overpowered. I've been chomping along at ramming speed down Walworth Road and had them zoom past. It's a bit incongruous seeing them overtaking, they're basically like a kid's scooter that's been fed a couple of doses of steroids. How dare they?
That said, I expect there's no evidence as to the dangers. I'll admit that left on pavements they would pose a trip hazard, and that scootists roaring along pavements is likely dangerous and unpleasant, but really you'd have to find a section of pavement that's not unoccupied by a car (moving or stationary). There seems to be a ironic blindness to the RNIB concerns at times.
(Personally, and I think the evidence supports me, I think anything that gets anyone out of cars, will reduce the damage, danger, and injuries – let's give people quick and easy ways to get around that don't involve the singular use of 3 tonnes of metal.)
ETA: probably I'm also misunderstanding what an e-scooter is.