You can't really "mute" a murderous mob that shows up at the capitol. This isn't about seeing stuff you don't like, this is about a platform being used to directly incite political violence.
There are many other possible attackers who won't be coordinating themselves on social networks in the open.
Capitol et al. should have robust enough security to keep most threats out, because some threats just won't be easily predictable in advance.
If I orchestrate a criminal conspiracy to rob Fort Knox, it is still a criminal conspiracy when it eventually fails.
And it should have.