There are probably more reasons you may have gotten a D- for it--I'd think a fair professor would have allowed such an argument assuming it was well-thought-out

There are probably more reasons you may have gotten a D- for it--I'd think a fair professor would have allowed such an argument assuming it was well-thought-out. There are of course plenty of professors (especially in philosophy) who give out grades based on how thoroughly they feel their egos have been stroked. Shame on them. Grades based on sycophancy are no different than any other kind of corruption.