You've only slowed it down--"
One of my favorite movies, with a few reservations, is called Antitrust. It came out in 2001 and is a movie of a college-age computer geek who goes up against "the" computer geek of the day, a guy apparently supposed to be bigger than Bill Gates, and almost certainly very much inspired by many people's ideas of him, dealing as it does with monopolies, antitrust laws, and ripping off other people's ideas. At the end of the movie, when the hero, Milo, has checkmated Gary, Gary basically tells him his victory is futile; he's only slowed down an inevitable force; other's will take up where Gary left off. Milo's come-back is a good one: "I slowed you down, Gary; that's what matters to me."
It's easy to think our job isn't done unless we put an end to the evils of the world once and for all, so our children won't ever have to deal with them, and that's certainly a good goal to have. But the truth of the matter is, we're only humans in a fallen world, with enough other humans on the opposing side to make it an endless battle. If, at the end of our day, we can say we've slowed evil down, than I would say we've done our job well. Leave the ultimate vanquishing up to God. Their day will come; it's just a matter of time.