I thought about that a bit why many maemonians detest SailfishOS on the basis that it has proprietary parts. Yet turn a blind eye on the fact that maemo has lots more of it.

I came to the theory that the reasons are historical. Back when maemo came around, such level of basing a mobile product on open source software was unprecedented. Things are not the same today, while SailfishOS is more open source than maemo, it is not amazingly open source compared to the rest of the mobile field.

So taken the time maemo and SailfishOS arrived, you could argue that maemo was more open source compared to the playing field back then than SailfishOS is compared to today's playing field.

It's a bit unfair, but understandable psychological reaction.