I don't see why it would bother a decent professor to be critiqued. Students pay an enormous amount of money to attend college, it's good to have a little insight before one commits to a specific professor's course. Most students are smart enough to take these ratings with a grain of salt and cipher out the spiteful posts. Although, when a professor has several complaints it becomes quite obvious that there is some truth to the reviews.
We all get rated and critiqued on our performance, in school and with our jobs, professors should be no different. I don't think anyone really likes to be critiqued but it is helpful and should be used as a tool to improve performance.