It's also known that people are not very good at assessing risk. People are more word about dying at the hands of a serial killer than they are of dying in a car crash or slipping in the shower. I feel you're underplaying the psychological harm of having all of your data crawled through by a creep (that would include all of your photos, sites visited, messages sent, everything).
All I can really say is that if someone gained access to my machine, the camera would be the least of my concerns. That's true in nearly every context (psychological, financial, physical, etc).
It's not just about nudity and extortion, but someone having access to watch you, whenever they feel like, in your safe space. That sense of violation that people also feel when (for instance) they have been the victim of burglary - the missing stuff is often secondary to the ruined sense of security. There's a vast difference between leaving your curtains open and having someone spying on you from inside your own home.
Is it rational to put this above other concerns? That's a whole different debate and not one I'm particularly interested in. But it explains why people are concerned about cameras over 'mere' data intrusion.
I presume the reason behind this is that video is much more likely to be re-shared. Sending bob a zip of someone's inbox is unlikely to be opened, and even less likely to be shared with strangers. But send bob a video of Alice, and he might open it. Heck, he might not know what the video is until he opens it. So even if he is decent, he might still see it. And if he is less decent and shares it, strangers are much more likely to actually view it.