premise 1: X criticizes YLet's be more specific:
premise 2: Z criticizes Y
conclusion: X is "in league with" Z
Sandwichman likes Harold Rosenberg's critique of party Marxism.
Joe McCarthy was also a critic of Marxism.
Therefore Sandwichman is "in league with" McCarthyism.
By the same token, of course, anyone who objected to Sandwichman's tacit alliance with McCarthy could be accused of being "in league with" that other Joe.
It's all so complex.