Fighting things that a lot of "normal" people don't like is always the cover. Whether that's fighting racists, mass shooters, pedophiles, drug dealers, thieves, etc.

The subtext is always that 90% of it is to go after enemies of the ruling class i.e. left-wing activists who are doing effective action out in the world.

You can see how vague their use of "domestic exremists" is. And of course they never show their work and provide statistics on their monitoring activity.

The article has a section here detailing it:

since 2019 the U.S. government has employed five domestic terrorism threat categories. These are defined by the FBI and DHS as racial/ethnically motivated violent extremism, anti-government/anti-authority violent extremism, animal rights or environmental violent extremism, abortion-related violent extremism, and all other domestic terror threats.

1. Ambiguous whether they're targeting ethnic minorities for hating whites/"Americans" vs. white spremacists (it's the former).
2. Ambiguous whether it's left-wing activists or just sovereign citizen types (it's the former)
3. left-wing activists
4. Ambiguous whether it's pro-abortion activists or the people literally attacking abortion clinics (it's the former, even though the latter is implied)
5. "all other domestic terror threats" (left-wing activists not covered under the former definitions)

Always gotta assume the worst.