Sarah Palin’s claim that her native Alaska wouldn’t put up with “the antics’’ of Scott Brown invites an obvious retort: Massachusetts wouldn’t swallow the antics of Sarah Palin. Not for a minute. With all respect for her impressive role in stimulating grass-roots interest in politics, she’s way too erratic and extreme for mainstream America. Only the most besotted Palin adherents fail to see the self-interest in her decision to quit her job as governor less than three years into her term. So the big surprise in this week’s contretemps isn’t that the loose-lipped Palin would slag Brown, but that seemingly no one in the Massachusetts GOP is willing to fight back. Yes, there’s a certain dignity and decorum in refusing to respond in kind, but national characters like Palin are a serious impediment for Republicans in Massachusetts. Until the state party makes clear where it disagrees with the Palins and Newt Gingriches and Rush Limbaughs of the national right, it will remain a minority in Massachusetts.