<--- exception to the rule, I felt a lot safer on my motorbike at 200kph than I ever did on any road/tri bike above 25mph, there is just no comparison, yeah, you are going much slower but

a) you are way higher on a road bike than you would be on a motorbike, extremely different centre of gravity
b) a motorbike has suspensions, which makes a big difference when taking turns on non perfectly smooth roads
c) a motorbike's tires are what, 20 times wider at least? my back tire was huge and gave me a lot of confidence in fast turns
d) a motorbike has 2 big disc brakes in front, stopping power is not even comparable
e) on a motorbike you wear a nice protective 'skeleton' under a nice suit, on a road/tri bike you have only a thin layer of lycra between you and the pavement, also the helmet protection is not even comparable once again
f) on a motorbike you always have power in reserve, if something happens you can quickly accelerate out of the way, on a bike it's dodge or crash, which limits your options
g) never felt a 'high speed wobble' on a motorbike, if a motorbike ever had that it would not be sold, but for some reason people seem to take that as 'normal' on a road bike

if at all I would think that people used to a motorbike would be even more scared than non-motorbikers on a road bike... I am also not sure about the skiing thing as I can go quite fast in downhills (ok, not as pro-fast, but reasonably quickly) but again the feeling is way different due to much lower centre of gravity and from being on two fairly long edged skis, which make turning and stopping a LOT easier