"The definition of a gadol be'Yisrael is one who is great in Torah and great in piety, one whose personal views and conduct are based exclusively on those twin pillars. Such a person is acknowledged as a peer by the other great men of his era. Rabbi Samson Raphael Hirsch was revered by the Chassidic leaders of Galicia and by the rabbis of Lithuania. That his views did not accord with theirs was immaterial; his philosophy grew out of his G-d-fearing understanding of Torah, and therefore it was legitimate for him. So it was with Rabbi Salomon Breuer and so it was with Rabbi Joseph Breuer. Their greatness transcended community. They belonged to Klal Yisrael, so they were honored by Klal Yisrael, all of it."
Rabbi Shlomo Wolbe
From Jewish Observer Article