It is hard to see how the speed of a computer relates to any sort of ethical problem. A slow computer is not ethically better than a fast one.
The only issue I can see is that computers with more speed allow us to do more things that might be unethical. The best example of that is probably pirated music and film. In the days when computers had dialup connections to the internet, there was not much chance of downloading a good copy of a movie. Today, with fast computers and connections, this is a possibility.