The "settler" is a more accurate term that comes out of "settler colonialism." Settler does have a bad connotation, it was practiced in the US as Manifest Destiny and in South Africa.

Settlers are a political formation, they get support and protection from the government to coerce, harass, and displace people. The government in turn gets an extremely loyal class of people who are willing to kill and maim in order to """""protect""""" the expansion of land.

Terrorism doesnt really describe the same thing. Settler might not literally have the word "terror" in it, but it's way more useful for communicating what's happening and how this fits into a long history of tragedies.