1. To spy on foreign nationals the FBI needs to get a judge approved FISA warrant based on evidence, then they can use the 2-hop rule to spy on those connected to the target.There is due process – starting with evidence of criminal wrongdoing by rightwing domestic terrorists.
Based on that objective, documented, constitutionally gathered evidence, rightwing domestic terrorists are lawfully investigate by law enforcement.
2. You cite generic "evidence", but don't really have any against "right-wing groups". The OP cites a "massacre" from 2019. IMHO the FBI needs to be defunded until they understand that they need to stop the partisanship, and to do their job fairly. Currently they coverup for democrats and fake evidence to prosecute Republicans.