It is like when you re-read a book, years later. You are both relearning what the book or the documentary tells you, and noticing how you feel about it 'this' time.
I've been doing a good deal of this late rereading books (making my way through Robertson Davies' oeuvre at the moment) and then this morning I showed one of my classes the great Nancy Nicol documentary, Stand Together from 2002.
It recounts the gay rights struggle in Ontario from the 60s up to the 1980s. The central driving force of the film is the struggle to include sexual orientation in the Ontario Human Rights Code. We learn a good deal more, with important tangents from side to side, and great cameos from different people of the era. This push for legislation is the struggle of the film, what keeps it moving forward.
What a good film it still is. As far as I know it's not available online, but you can see a trailer here.