Take a moment to consider:
This is the same CloudFlare that previously agonized publicly about their decision to terminate service to The Daily Stormer, a neo-Nazi white-supremacist web site whose views are thoroughly repugant to every decision maker at CloudFlare, and probably equally repugnant to the vast majority of CloudFlare's employees and customers. Nevertheless, the Daily Stormer decision so disturbed CloudFlare's CEO that he immediately started laying groundwork to never have to censor again. But censoring scientific research, for copyright reasons? That apparently doesn't fall into the same category.
Don't blame CloudFlare, and don't even blame the American Chemical Society. They're not the problem here. The problem is that a limited state-granted monopoly has been expanded -- at first gradually, then suddenly -- by major media companies and their servants in the legislative branch to the point where censorship in its name is considered perfectly normal, so much so that using it to censor scientific papers is less worthy of hand-wringing than censoring, say, a neo-Nazi white-supremacist web site.