The big difference is that CS is not the user. In you analogy it's like your car allows you to drive off a cliff, and an (almost) essential part of your car (for example, the pedal) drives the car off a cliff.
It got there because a user or administrator approved and installed it. It didn't just appear there, Microsoft didn't install it there. The user ran it.
Right, so a slightly better analogy would be if you wanted to install a remote starter, but then you find out that they can only be installed into Fords, because other auto manufacturers (Apple, Linux in this case) believe that tampering with the critical path (the engine, kernel) is unsafe. It isn't Ford who's at fault for allowing you to run some random engine modification, it's that mod that is at fault.
It got there because a user or administrator approved and installed it. It didn't just appear there, Microsoft didn't install it there. The user ran it.