Apparently, he even considered converting to Christianity at one point:
And yet, I know of no one who defended Judasim from the attack of anti-semitic Christain scholars with more passion (See at length S. Heschel - Geiger and the Jewish Jesus - what follows are excerpts from that book.):
Finally a quote from Wikipedia concerning his stance in the Damacus blood libel affair,
Geiger's opposition to a Jewish national identity was also sharply criticised, most notably an accusation made that he refused to intervene on the behalf of the Jews of Damsacus accused of ritual murder (a blood libel) in 1840. However, Jewish historian Steven Bayme has concluded that Geiger had actually vigorously protested on humanitarian grounds.