One of the things that has been a constant part of Sesame Street over the years is content delivering variations on this message: "There are many types of families. If yours doesn't happen to include a mother and a Father, that doesn't make you weird, it doesn't make their love any less."
Going back to the early seasons, there were montages of children being raised by their grandparents, a single parent, an aunt or uncle etc. The message that there's nothing wrong with a family of two daddies or two mommies and that such a family is absolutely normal and just as loving as any other is absolutely and unquestionably in line with their mission and their previous messages.
Further, the fact that a family has two mommies has no more to do with teaching children what people do with their genitalia than showing heterosexual parents does.
Yes, it might piss off some ******* bigots. So would showing interracial friends when it first aired, but they did that too.