By the time the pro-Palestinian demonstrators showed up in front of Houston Mayor John Whitmire’s house one night in mid-September, the cops had been awaiting them for at least an hour. A dozen or so young men and women lined up on the sidewalk as roughly the same number of Houston police officers watched impassively, standing by their cruisers. The protesters were aligned with activists who had been pleading with Whitmire and the city council to pass a resolution calling for a ceasefire in the Gaza Strip and to disinvest from Israeli interests. Most of their faces were covered with masks or keffiyehs, the distinctive scarves that have become symbols of the Palestinian liberation movement.They chanted at roughly the same volume as kids in a…