By having each redundant flight computer hooked to completely different sensors, in case of a bad sensor the crew can bypass not only the sensor, but also any computation done with that sensor.

It's not a single point of failure as we think if it - if it starts acting up, you can easily disable the automatic stabilizer system, per the procedures. 737 stabilizer runaways take several seconds to take effect, and are recoverable afterword. Later you can switch flight computers and then be using clean data, though you are supposed to leave the stabilizer system off for the remainder of the flight.