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.

TBH physical security of vital structures like Capitol should not rely on someone's ability to moderate some platform.

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.

Regardless of how well the Capitol is guarded, inciting violence is still a crime.

If I orchestrate a criminal conspiracy to rob Fort Knox, it is still a criminal conspiracy when it eventually fails.

The Capitol has its own police (they're literally called, the Capitol Police). You can't mute them, but you can make it clear that any attempt to breach the Capitol will result in deadly force.

And it should have.