I hope your definition of evil is yours alone. However, it isn't. You got your definition from others I'm sure. You believe in evil because you were taught it. Many people think as you do, and it leads to war. Both sides are trying to stomp out the force of evil. They don't realize evil doesn't exist. If they did, nothing to fight about. Those who believe not in evil, have no reason to rape, pillage, steal, rob, whatever. Just doesn't happen. Those who do, need to do that stuff.
You're assuming a lot about me that just isn't true. I've actually given the subject of evil a lot of serious thought and study, both within an academic setting and on my own. The definition is my own.
Most people acknowledge the existence of holy men and women, people within whom good is extremely concentrated and has taken on something of a life of its own. They shine with inner light. If you want to deny their existence, I guess that's your right, but you may miss the benefit of being in their presence.
The opposite exists as well. It must exist. Sadly, evil is there whether one wants to acknowledge it or not. (Not believing in evil has led to plenty of disaster and tragedy, too.)
Recognizing evil as a force or energy that is present and active in our world is not the same thing as signing on to a crusade to "stomp it out." Unfortunately, it doesn't work that way. I wish things were that simple!
Evil is more like the spiritual, moral, emotional, energetic equivalent of rotting food. There is no scientific definition; I don't see how there could be. But that hardly makes it a useless concept. Nor does it excuse participants from responsibility.
And in some ways, real concentrated Evil-with-a-capital-E is rarer than people think. That terrorist guy is a somewhat ordinary kind of evil. There are plenty of people in this country who say the same kinds of things. But look at how this man speaks. Look at his face. It is like he is possessed. Not all evil people act in this particular B-movie way, but when you see someone really doing it, it's rather unmistakable. But it is not a scientific observation. It is a psychic one -- as in pertaining to psyche. There are a lot of tools in there we generally do not use, but they are very helpful.