Quoting from Wiki: "By the end of the 20th century, a new, pejorative use became prevalent in some parts of the world. In the Anglosphere, this connotation, among younger speakers, has a derisive meaning equivalent to rubbish or stupid (as in "That's so gay."). In this use, the word does not mean "homosexual", so it can be used, for example, to refer to an inanimate object or abstract concept of which one disapproves."
In other words, he just meant it was a crap idea!