WASHINGTON — You have perhaps heard the joke about the liberal who is so open-minded that he can’t even take his own side in an argument. What’s less funny is that on gun control, liberals (and their many allies who are moderate, conservative and non-ideological) have been told for years that if they do take their own side in the argument, they will only hurt their cause. Supporters of even modest restrictions on firearms are regularly instructed that their ardent advocacy turns off Americans in rural areas and small towns. Those in favor of reforming our firearms laws are scolded […]