Why is Casaubon in favor of Catholic Emancipation?

Here's a question I put to my graduate seminar earlier this week. 

While joshing Mr. Brooke about his friendly relations with Casaubon, Mrs. Cadwallader snarks that

"I see you have had our Lowick Cicero here [...] I suspect you and he are brewing some bad politics, else you would not be seeing so much of the lively man. I shall inform against you: remember you are both suspicious characters since you took Peel's side about the Catholic Bill. I shall tell everybody that you are going to put up for Middlemarch on the Whig side when old Pinkerton resigns, and that Casaubon is going to help you in an underhand manner: going to bribe the voters with pamphlets, and throw open the public-houses to distribute them. Come, confess!" (Middlemarch I.i.6)

Peel's ultimate support for Emancipation was, of course, one of the great political flip-flops of the Victorian period.  Now, Mr. Brooke's decision to follow Peel (and, we're told, to let the local Roman Catholics erect a chapel on his land) emerges from no great philosophical devotion to reform, modernization, or anything else.    As he explains at the fateful dinner with Casaubon, "the Reformation either meant something or it did not, that he himself was a Protestant to the core, but that Catholicism was a fact; and as to refusing an acre of your ground for a Romanist chapel, all men needed the bridle of religion, which, properly speaking, was the dread of a Hereafter" (I.i.2).  This typically vague and self-contradictory chain of reasoning (what "something" does the Reformation mean? what precisely is the relationship between "fact" and toleration for a purportedly committed Protestant in 1829?) finally issues in a purely utilitarian view of religion as a means of social control, with Protestantism and Roman Catholicism having identical effects.  (So much for the Reformation, one takes it.)  Unlike Dorothea, Lydgate, Will, and, indeed, Casaubon, Brooke rarely registers the deep historical discomfort that permeates the narrative; here, he seems not to understand the cultural and religious seismic shift of which he has made himself a part.  (It's no accident that Eliot begins the novel shortly after the bill passes--this is a book about the coming of Victorianism, so to speak.) 

But why does Casaubon support Emancipation? Mr. Cadwallader comments that Casaubon's position was "unexpected" (I.i.8), which certainly doesn't help matters; it does, however, link him (and probably Brooke as well) to Peel.  There's nothing in Casaubon's behavior elsewhere in the novel to indicate that he finds politics particularly interesting, and there's less than nothing that would lead us to suspect him of hidden liberal or pro-reform leanings.  The most obvious temptation, then, is to read Casaubon's startling pro-Emancipation stance in the light of his problematic relationship to both historical thinking and modernity (and, possibly, to what is clearly a failed vocation as an Anglican clergyman).    Casaubon's lack of interest in Emancipation's political ramifications, for that matter, looks like another symptom of his notoriously "dead" historical narrative, which remains shattered in permanently disconnected fragments.   In a way, he might be the flip side of Mr. Brooke: Brooke begins by alluding to history (the Reformation), then jettisons it for pragmatic reasons; Casaubon, who "live[s] too much with the dead" and suffers, like Dorothea, from symbolic bad vision (I.i.2), appropriates the topic for yet another one of his endless tract productions.