Is there anything wrong with using the NSA and CIA for surveillance of domestic terrorist groups like antifa?

People often say" oh mass surveillance is terrible", and obviously it can be abused like anything, but is there anything wrong in principle with using it to monitor violent left-wing groups and in that way stay ahead of them and prevent their violent plans and actions? CIA focuses so much on foreign threats, but that seems a mistake to me, it should do both. What do you think?