In Paris, police used tear gas to push back protestors when a demonstration by opponents of gay marriage turned violent following a vote by lawmakers to legalize same-sex marriage in France. The demonstration reportedly started peacefully, but eventually some rioters threw glass bottles, rocks and even small, “petrol bombs” at police following the vote by the National Assembly. The issue of gay marriage is a contentious one in the European country—polls show a sharply divided population with many social conservatives displeased by the decision of the Socialist-majority Assembly. Last week, New Zealand also passed laws legalizing gay marriage …