"The pretext of the raid was that two individuals from the group had reportedly sent out “simulated court documents” — summonses for a judge and a banker to appear before the Republic of Texas to discuss the matter of a foreclosure.
These “simulated documents” were rejected and the authorities decided to react with a “show of force” — twenty officers and an extremely broad search warrant."
Ah, do be careful when attempting to overthrow the government, it tends to overthrow you, off the nearest bridge. And be careful who you associate with, they may be the wrong kinds since fringe movements like this are full of nutters.
There are dangerous fringe groups out there, this does not appear to be one of them and it does present the image of overkill on the part of Law Enforcement.
Given that I'd like to get more from the side of the raiders and why they determined this style, level of raid was necessary, there could be other unreported aspects here that justifies what Law Enforcement did.

By law if someone
is not advocating the
use of force or violence to overthrow the Federal government, any local, county or state government he/she/they are withing their rights as protected by the First Amendment however if they are participating in other actions that are illegal then it's a whole nother story.
No one was arrested so this has all the appearances of an intimidation tactic which would constitute a violation of their Civil Rights. Personally I believe (I have a law enforcement background) those who ordered and orchestrated the raid have some explaining to do.