Mass killings today are often part of a broader online network — either officially or unofficially — of enablers who push potential perpetrators to commit acts of violence in public. Under the current law, whereby domestic killers are charged only under regular criminal codes, police are unable to go after those who are egging on and supporting domestic terrorists. If these dangerous actions are designated as terrorism, not only will police have more resources to investigate killings but work to prevent them in the first place.
Violent acts should be punished, but broadening the definition of terrorism would go beyond acts and criminalize beliefs. US law enforcement has already discriminated against Muslims by quickly deeming them terrorists while their non-Muslim counterparts are "lone wolves." However, broadening the definition to allow the government to oppress more ideologies linked to past violent attacks — from animal rights activists to White supremacists — would only create a more dystopian and intrusive police state.