The DOJ is fighting to have civil-rights era cases dismissed in an effort to segregate the schools again. They have claimed that racism no longer exists, and so those landmark cases are no longer necessary.
This memo not only mobilizes the police to target people, it uses the full force of the entire intelligence apparatus to investigate and prosecute voices of dissent.
Between the national protests, there are lots of local activities that you can be involved in, as well as other related activist groups who organize their own anti-Trump actions.