First, congrats to them. But I'm not sure if 51 years is so very remarkable - we have 50-year-plus couples featured in our Stonewall Pride parade every year.
But it's true about gay bars once being owned, and given protection, by the Mafia. That's who owned the Boston clubs, when my partner lived there. But police raids could still happen, so there were early-warning methods to minimize arrests when the vice squad suddenly appeared. It's fascinating to hear his stories about how things were for gays back then.