Massachusetts lawmakers June 14 voted to kill a proposed constitutional amendment to ban same-sex marriage, leaving opponents of such marriages discouraged. The state legislature, meeting in a joint session, voted 151-45 to block the proposed amendment from being placed on the 2008 ballot. The citizens-backed measure needed five more votes, 50 in all, to make the ballot. Governor Deval L. Patrick, a Democrat who took office in January, said the vote was a victory for equal rights. “In Massachusetts today, the freedom to marry is secure,” Patrick told a cheering crowd of supporters at the statehouse after the vote.