Sometimes I think maybe it's my own bias, but I notice the same thing on their parent site, Amazon. A whole lot of times lightning deals, recommendations, etc., have t-shirts, mugs, and whatnot with liberal talking points and wise-ass remarks. If you go to the deal page, you'll see that most times the same company also has stuff with the opposing political view, but I never see that side displayed on any of the "click me" pages.
While Woot may skew more liberal in the customer base, I would SWAG that Amazon is fairly evenly distributed in the politics of the user base, so you'd think they'd be a little more careful in showing a bias one way or the other.