No one denies that a non-Catholic will have error mixed in with his views. It is a matter of degree. Yet such a person might express himself on particular matters in an orthodox sense, and more eloquently than a Catholic. John Wesley preached many sermons which would be of great benefit to Catholics, as he possessed almost identical beliefs with regard to things like sanctification, regenerative baptism, the perpetual virginity of Mary, Christology, etc. John MacArthur have many fine and beneficial insights to offer, for the discerning and careful Catholic reader.
Truth remains truth, even if it is surrounded by erroneous propositions and statements.
But my general policy is to not link to anti-Catholic sites. But this is irrelevant. Influences are not the equivalent of dogmatic or papal pronouncements. We have reason to believe, e.g., that the early Church was influenced by Jewish liturgics and sacred architecture. This goes for the New Testament also.