Well, unsafe if there are cars all around you. But if we replaced a lot of cars with these vehicles which typically go around 40 to 70 km/h cruise speed, I think it would become way safer than cars.
A colleague of mine has one. They are easy to overlook and he sometimes has pretty bad looking crashes (from the outside) but the chassis themselfs are extremely sturdy and protecting. He slid down a road 25m at one point, crashing into a pole, but only got a bruise from it. Because, and that's the main point: these things are not going down 50mph, they are at 18mph and the only dangerous parts are intersections where cars are slower anyways
separation of bikes and cars are rare in my city/country, and traffic tends to be very chaotic.
the main reason i say these look unsafe is that they look way less maneuverable for this situation. the nimbleness my bike has helped me avoid pretty gnarly accidents a couple of times before.