This T-shirt beef is getting nuts! “I don’t know how to use the mind of a squirrel,” Marilyn Manson, 48, declared recently when asked what Justin Bieber, 23, was thinking when he hawked $195 T-shirts featuring the “Beautiful People” singer’s face without his consent last year. The pair have been feuding over the Purpose tour merchandise ever since, especially after Justin reportedly claimed, “I made you relevant again” as a jab at the none-too-happy Goth rocker. And while Justin handed over all the shirts’ proceeds and even apologized, Marilyn clearly isn’t ready to bury the hatchet. “I don’t like to fight with girls, so I don’t wanna fight Justin Bieber,” he snarked on the syndicated radio broadcast The Scully Show . So it appears that for these…