What's more is that Malthus played an instrumental role in inspiring Charles Darwin's thinking on natural selection. Now, in some corners of America today perhaps that's another mark against him, but I think that's fairly substantial!
What's also ironic is that while his essay on population had perhaps the widest impact through its influence on Darwin, it was his work on political economy that has probably had the most impact on economics. Malthus was the premier proto-Keynesian. I worry sometimes that Keynesianism suffers from its associaiton with Malthus because people irresponsibly brand environmental doomsday prophets as "Malthusian".
I'm not sure where to go with that of course. It's just one of those instances of bad PR that the victim - who is long dead - can't do anything about.