They’re not telling anyone “how to think”. They’re telling transphobes and “trans sceptics” to fuck off. And who cares if they do it with a pinned post rather than a sidebar announcement? Some apps hide the sidebar in a menu.
Also when you say you opened a bunch of communities, do you mean you hosted them? Because those two women are literally running the server this instance is running on. Doesn’t sound all that easy to me.