Taibbi is funny, but I wish he would be a little more careful in some of his more colorful language (in particular, the "tranny cabaret" remark and the "hairy hunchback" phrases).
His argument is straightforward. When we laugh at Bachmann, there is a distinct minority of the electorate which wants to defend her, because they're getting laughed at all the time, too. Taibbi's fear is that, in the event of a pre-election double dip (Wall Street melting down a second time and unemployment rising), votes against Obama/status quo might turn into votes for Bachmann.
I do not find that fear plausible. I also don't really believe she'll win the Republican primary, but I guess we'll find out in the next few months.