I'm surprised that you are surprised. The masons derive from the stone masons who travelled more or less freely in western Europe in the middle ages--a time when most people were serfs and didn't have that kind of freedom. Eventually, the masons founded a fraternal order, whose view points were informed by the natural liberalism of the original masons (liberalism in social outlook, that is not a reference to contemporary American political idiocy).
Many of the Founders were Freemasons, including George Washington . . .
. . . that's an image of Washington in masonic regalia, laying the cornerstone of the capitol building in 1793.
Many of the loonier right-wing groups, especially among fundamentalist christians, now allege deep and nefarious plots among Freemasons, and in particular the Founders--alleging that SATAN took over the nation from the day one. It's easy to find their web sites, and they are often really hilarious. In particular, they seem to be outraged by the masonic symbols on the dollar bill.