The first thing that many people think of when they hear settler is a guy with long peyot and big kippah. To those who've really given in to the trendy UN narrative, they'll see the settler the same way your average new York Times reader see an Israeli. Violent and bloodthirsty etc etc.
Who are they really The settler movement is anyone who has the ideology to expand Jewish settlement in the ancestral heartland. (Notice how you can change settler to Zionist and the meaning stays the same) It could be those living in established settlements and cities such as Ariel, Efrat or Ma'ale Adumim or those starting new settlements on strategic hilltops.
Why Like any Jewish Zionist is the desire and G-D given right to settle in their ancestral homeland "Our deed to the land is the bible" Additionally, anywhere without Jewish presence in this land, terrorism festers as we saw after Jewish people were forced out of their homes in Gush Katif in 2005. Before Smotrich came into the government, Palestinians were illegally building on state land closer and closer to Jewish populations, commiting more and more terror attacks.
Now farms and new settlements have been built in strategic areas overlooking central junctions and Jewish population hubs that were prone to terror attacks and guarding large swathes of land from terrorist activity and illegal infrastructure.
Something that would surprise people going there is the coordination with the army, and how every Palestinian attack on these settlements almost always gets spun from a story of Jewish self defence into a story of settler violence against the "helpless" terrorist.
I hope the next time you hear the settler violence blood libel come up, you'll defend those who live with terrorists by their doorstep so you don't have to.