It looks like the ACM General Elections are coming up, with several officers and various other positions being available:

https://www.acm.org/elections/acm-council/2020-slate

It's likely worth someone contacting each of the nominees to publish info on where they stand on the Open Access issue.

With that, the general ACM members who vote should have a decent ability to affect the ACM's future directions on this issue. :)

That is assuming not 100% of all nominated people are against Open Access. Could be a bad assumption though. :(