I won't argue against the importance of visibility, but I think it's secondary to the actual existence of the data in the first place.
One of the defining qualities of blockchain tech in general is censorship resistance. It's also a major part of Steem, and a big draw for many people including myself. I'm confident that those of us who care about this issue will find a way to leverage that quality come hell, high water, or front-end censorship.
"Force" is a strong word. Surely you can work to demoralize someone with flagging, but that does not directly stop their posting. That's only going to stop people who come for entertainment and frivolity, and those who have no reason or will to persist in demoralization. Those with conviction, like whistleblowers or watchdogs as extreme examples, will retain the unfettered ability to transmit their content around the world even when all their posts are flagged to zero. No other account could stop them or stop anyone from reading their content.
This, I think, is powerful. Much more powerful than any frontend.