"A substantial and growing number of Americans say that Barack Obama is a Muslim," not that there's anything wrong with that

James Taranto in the WSJ's "Best of the Web" is always quotable, and this line caught my eye (homage to "Seinfeld")

"A substantial and growing number of Americans say that Barack Obama is a Muslim," not that there's anything wrong with that, according to a new poll by the Pew Research Center for the People and the Press. Eighteen percent of those polled think the president is a Muslim, up from 12% in October 2008. The Ground Zero mosque doesn't explain this shift, as the poll was conducted before he stepped into that controversy.

Of course the Left will blame Rush or Glenn Beck.  But like the accusation of being gay, aren't Muslims practicin the "religion of peace?"  What's wrong with that?  Would it be an insult to call Obama a Catholic?