Now I'm confused. If Arp is such a bad scientist, and Max Plank Institute is such a prestage facility, how is it possible that he found work there?
You are assuming that Arp is a bad scientist. Well, he's not the greatest, that's for sure, and he's made some mistakes of fact and some errors of judgement; but he's done some good work and appears to be continuing to do some good work.
It's also possible (just off the top of my head, and I have no idea if it's true) that the Max Plank Institute is purposefully employing him to ensure that alternative viewpoints are investigated and heard. The "monolithic and dogmatic" scientific establishment is a myth.