Warning, the JPMs in this post are high.
One of the most evil philosophies of this time is the so-called "balance of good and evil" that I have seen some people advocate with complete sincerity. I am not talking about the Biblical concept of not being able to know joy without sorrow, etc. which is absolutely not the same thing; I am talking about the concept that too much good is just as bad as too much evil. This is reflected in the "parallel world" story of popular fiction where there exists a world that has to be the exact opposite of ours for there to be balance. I know (almost) nobody truly believes this, but I do know people who absolutely believe that the concept of Heaven is abominable because it would be "so boring."
Evil is not to be countenanced and we should always strive for good—to make the world a better place for all people. We can make it a better place and we can do better. Always look within yourself and work to overcome your own flaws, then work to overcome the evils in this world. Be supportive and loving toward others, rather than hateful and judgmental.
There is no such thing as "too much good" or "too little bad."
I find it abhorrent when people justify bad things by saying "it is God's will," and equally abhorrent when people take risks with their own lives and justify it by saying, "if it's my time there's nothing I can do about it," with the implied corollary that a person can't bring about their own death when it's not their time. This is not true! God has a plan for us, yes, but we can destroy that plan because we do have free will. We can destroy this plan for others as well, which is why murder is such an abhorrent sin in God's eyes. There is enough risk in this world already without us making foolishly risky choices with our health and our lives.
It is true that it is God's will that we be tested in mortal life. It is true that the world is not perfect and that is by design, but this is the case so we can overcome, to build ourselves and others up, so we can face God in the end have Him say, "Well done, good and faithful servant; thou hast been faithful over a few things, I will make thee ruler over many things: enter thou into the joy of thy lord." (Matthew 25:23)
A truly evil philosophy that I have seen Christians espouse is the false version of the Doctrine of Grace. In this version it is seen that we literally can't do anything to save ourselves, and that it is purely the salvation of Christ that saves us no matter what. What makes this so pernicious is that it is so close to the truth that people accept it, and then feel like when they do wrong, it's actually okay as long as they have "accepted Christ as their savior."
The problem with this is that while we cannot save ourselves, we can certainly turn away from the salvation of Christ in many ways, even if we still believe in Him. Jesus gave us a blueprint of things He expects us to do, and without an active effort to work toward those things we are effectively walking away from His salvation. It is summed well by James 2:26, which says that "faith without works is dead."
We cannot say we have accepted Christ and His salvation if we are not doing our best to do as he has asked of us; we cannot be perfect no matter how hard we try, but we should always strive to be better.