"One of the annoying things about philosophy is that the dead simply don't die. Once a philosopher or philosophical doctrine gains some celebrity in the community, it's very difficult to convince anyone afterward that said philosopher or doctrine was flawed. In other words, the philosophical community tends to have problems with relinquishment. Therefore, there are still many philosophers that spend their careers studying, for example, Plato, apparently not with the intent to determine what parts of what Plato wrote are correct or still applicable, but rather with the intent to defend Plato from criticism. To prove Plato was right."

I don't know what kind of background you have in philosophy but in my experience this is just wrong. There is not a single philosopher in my department that fits this description and I have never met anyone who does. I'm not even sure where you get this perception. Its true that past philosophers are routinely referenced but this is just because its sometimes easier to use the concepts of ones predecessors rather than reinvent the wheel. But read any metaphysics written in the last fifty years and and you'll find dead philosophers are only used to refer to common positions or as less wrong theories that make decent jumping off points for better theories.