Wagner was a genius. He knew how to capture the whole sound and passion of opera. But due to some little corporal Wagners name will be forever tarnished as a Nazi! Even though he lived 60+ years before Hitlers time.
Not knocking Wagner at all, but the plain historical fact is that he did happen to be a very visceral anti-Semite, which doubtless at least partially accounts for Hitler’s admiration of his music.