At a demonstration yesterday in Boulder, more than fifty gay-rights advocates, joined by newly elected Congressman Jared Polis, raised their voices in protest against the Cinemark movie-theater chain, whose owner, Alan Stock, donated $9,999 to a California campaign to outlaw gay marriage. But the timing of the event made more sense nationally than locally. A boycott by an organization called No Milk for Cinemark! timed the rallies in Colorado and beyond to the November 26 opening of Milk, a Gu