In the end removing or keeping OtherOS might've been irrelevant, since the service-mode dongle showed up. People like to construct narratives around these events, though, and it sends a better message if they can say that Sony brought this upon themselves. (Well, they did by screwing up the crypto code, but I mean in terms of behavior regarding the PS3.)
Yeap, I don't think OtherOS is the crux of the issue. Sony's over-reliance on the Cell security is the key problem. There are folks who have been hacking PS3 for a number of years.
If Sony had been diligent about the security fundamentals, PS3 may get hacked one day but it won't fail so spectacularly (with fireworks and virtual symphony playing in the background).