Certainly on the cultural side they've added disproptionately to our society. As to in general, they hold many jobs in many walks of life that help society, including medicine. Same as the heterosexuals.
Or so they would have you believe. I think we'd be pretty much the same without them.
BS! To the extent that "culture" is valueless and amoral, I would agree ... they have disproptionately contributed in that area. But to the extent that roads, infrastructure, buildings, music, medicine, communications, government, and just about anything else that lays the framework for a culture and society, gays have contributed nothing outside of the roughly 2% that they comprise of the general population. And when you consider the healthcare costs, the degragation of morality and values, and the double-speak politically-correct thought-crime nonsense that they are pushing, I would posit that they are net-negative contributors to a healthy culture.