When Massachusetts enacted a gay and lesbian civil rights bill 30 years ago, opponents warned about the slippery slope of acceptance. Senator David H. Locke, a Wellesley Republican, called the bill “the opening salvo in the gays’ march to social acceptance and approval of their chosen lifestyle” and predicted it would lead to legislation “permitting men to marry men and women to wed women.” In hindsight, the bill’s chief architect, Arline Isaacson, has to agree. The 17-year-long campaign for the gay civil rights law laid the groundwork and set the playbook for every successful campaign that followed in Massachusetts.