Such opposition is reasonable. Someone has to fight against closed codecs. But fighting alone is hard. Google pretended to be the "white knight" when they promised that they'll drop H.264 support from Chrome, but they deserted the battle and didn't keep the promise. They could really influence the industry by dropping H.264 support from Youtube, but they don't have guts to do it since it's quite disruptive.
I'm positive that anyone who misuses the word "closed" to refer to patent encumbrance has never had to suffer through working with actual by-definition closed codecs.
You should have enough information from the context, to distinguish closed as "no known specs", from closed as "not free to use". May be the term non free / free (as liberated) codec is more descriptive, but closed/open will do as well.
See also https://hacks.mozilla.org/2012/03/video-mobile-and-the-open-...