Unlike you, he isn't jealousy of Bachmann, looking to hold a grudge and believes she has sufficiently renounced anti-Catholicism:
http://nymag.com/daily/intel/2011/07/michele_bachmanns_reverend_wri.html
"I believe [Bachmann] has in the past condemned anti-Catholicism."
Why not just come clean and admit you're trying to undermine Bachmann's candidacy because you're a Palin supporter. You'd at least come off as more honest that way.
Has Donohue - or any of the others - taken a similar shot at Romney? Are they happier with Mormon theology?