Has he ever attempted to discredit any religions other than Christianity?
—Has he ever attempted to discredit any religions other than Christianity?—
Why should he? He is doing Satan’s bidding. Satan’s only enemy is Christianity, and of course the deity they worship.
Dawkins treats all religions equally, but as he points out, because Christianity is the dominant religion in Western culture (the one in which he resides and which represents the market for his work), he often uses it as an example. But Dawkins is no more anti-Christian than he is anti-Islamic or anti-Wiccan. If anything, he is kinder to Christianity due to its more civilizing influence.