Try crashing into a wall at 30mph, 60mph and 90mph. See which does the most damage
I won't argue that on a completely empty, straight road, in a modern card, 100mph is probably perfectly safe. But this thread is talking about people doing 90 - 100mph on a busy motorway where people who are driving at 70mph need to pull into the outside lane to overtake, because all inner lanes are travelling slower than that. In those circumstances, I'd say that was inappropriate speed...