i am an intelligent person... but i still run software that segfaults occasionally (not code that i am developing). if there were no memory protection, such bugs could put the kernel in an inconsistent state, leading to corruption of the filesystem... or deactivating firewalls.
You don't have to be stupid or careless to fall victim to some of these things (although it helps), but if you turned off memory protection and proceeded to use your computer for every day online things, i'd say you were being stupid and careless.
I don't even connect my Amiga to the network at all these days now i have a SDHC card reader for transferring files to my PC.
Of course all technology can be used for good or for evil. But i don't find that memory protection limits me in what i can do on my own computer. I do find that Windows does.