What had Reisman against Rothbard?
They were in extremely friendly terms in the 1950s and when as a young student George Reisman provided a pro-McCarthy speech honouring Roy M. Cohn the speech was written by Murray Rothbard.
When Reisman became more affiliated with the randians and Rothbard wanted to disassociate himself from the randians, Rothbard wrote a paper which had many ideas similar to those written by Nathaniel Branden and Ayn Rand. There were accusations of plagiarisms and while Ralph Raico and Ludwig von Mises sided with Rothbard, the more pro-randian collegues of Rothbard, particularly Robert Hessen and George Reisman, had the opinion that Rothbard should mention Branden as the original author of those “plagiarised” ideas. That was the moment when their friendship was gone and it never fully recovered.