Why are liberals making a big deal that Michelle Bachman didn't know where the battle of Lexington took place?

Michelle Bachman gave a speech in new Hampshire and mentioned a couple of battles from the Revolutionary war ('Lexington and Concord) happened in new Hampshire. It turns out they happened in Massachusetts, but the liberal;l media found a 'gotcha' moment. Who cares??? Those were battles nobody ever even heard of- why does the left have to make such a deal out of such an unimportant mistake? They need to remember Obama thinks there are 57 states, and he uses a teleprompter.