If someone voices something different than what they want, they label them as communist extremists and create a fake group name like antifa to which they claim they were apart of. Which they already labeled antifa as a terrorist organization, thus giving them the ability to prosecute with no way to prove someone isn't in antifa, as the group doesn't really even exist unless it's 1930s Germany. Whether or not they end up being able prove your guilty, remember Trump during his first term stated he believed in taking away the guns first, and then doing the investigation. Mike Pence had to walk him back on that because it would be unconstitutional.

Call them unAmerican and take their guns; if they complain, throw them in Alligator Auschwitz

According to their fascist dogma, dissent is inherently treasonous, so they won't need any further justification.

Also, Wilhoit's Law applies:

Conservatism consists of exactly one proposition ... There must be in-groups whom the law protects but does not bind, alongside out-groups whom the law binds but does not protect

Why do you think they'll need to justify it?

With lies, like everything else

How did Taco "justify" DC?