The funny things is, you just described the premise of the game SNATCHER, and that came out in the 1980's.

In fallout 3, they're actually the odd ones out in the brotherhood of steel. They realized that the super mutants were a threat to everyone in the capital wasteland, and decided to use the technology they've gathered to defend the people of the D.C. area. Some in Elder Lyon's chapter were appalled, and broke off to form the Brotherhood Outcasts. Sometime after the change in objectives of the east chapter, the western ones, still forcefully taking technology from civilians, caught wind of Lyon's rejection of the codex and disowned them.