If the burglar was able to get into the home because the door or window was flawed, you bet I would blame the guy who built to door or window, and so would you.
But I'd be orders of magnitude more p*ssed at the burglar. Just because the door or window was flawed didn't mean he had to come through it.
It all reversed when it comes to computers. Everyone gets ticked only at Microsoft (and they are certainly far from innocent), but I see very little, if any anger against the purveyors of the spyware, malware, etc.
I guess a lot of it is that people are lazy. It's easier to hit the big target (Microsoft) rather than try to find who actually wrote the spyware or who put it on their computer. After all, it's their computer and they shouldn't blindly trust someone else to keep it secure.