No, there is nothing right with blocking someone else's plugin, even if it may be broken.
If you go down that road you are justifying MS blocking any other software from working on your computer just by blaming the other software to be unsafe.
... that is not far from what Apple does (and somehow google as well).
The computer is mine, it's not your problem if I want to use unsafe software.
I see what you mean, however it's their browser and they don't want crap to pass through it, then see you blaming the browser :P
\No, they just want to kill flash in favour of HTML5, it's different. ;)
If that were true, it's not really a dumb choice, you have to admit it anyway xD