Yeah, and they didn’t let him forget about that heritage, either. He never lost the North German accent, although the kiddies he gave candy to on his walks didn’t seem to mind it as much as their parents. It didn’t help that Wagner was so adopted by the Bavarians (Ludwig II especially).
From Jan Swafford's biography of Brahms:
The opening chorus's text from Revelation proclaims, "Hallelujah, salvation, and glory, and honor, and power, unto the Lord our God; for true and righteous are His judgments." Brahms omitted the Scripture's indecorous following lines -- "For He hath judged the great whore, which did corrupt the earth with her fornication." Privately, though, he copied the beginning of that verse into his own score, under an instrumental phrase that exactly represents it. He took great glee in pointing out the spot to friends.
Brahms was of two minds about the whole pan-German thing.