It is possible for a single symbol to represent good or evil, depending on which side you take or represent. In the case of a peace symbol, it was used by the Vietnamese to represent their anger and rage. The US uses it as a sign of peace, like an olive branch. It's most universally used as a peace sign nowadays, but it's origin was a sign of hate.
Just like there are two sides to every story, if you look at abortion, there is anti-abortion (life) and pro-abortion (choice). People who are anti-abortion or pro-life do not want to have abortions, anti has a negative underlying tone, and makes abortion sound like a bad thing to do. They try combating it with a different take on anti-abortion with pro-life to make it sound more positive, saving lives. On the other hand, there is pro-abortion or pro-choice, which has a positive underlying tone and has the opposite effect of anti-abortion. It sounds like abortion is okay and allows freedom. These are two different stances on one thing - abortion. This is similar to how there were two takes on the peace sign.
A good way to sum up this reading section is a yin-yang symbol. This symbol represents constant change in a circle. Day becomes night and night becomes day. Happiness becomes sadness and sadness becomes happiness. Birth becomes death and death becomes birth. Friends become enemies and enemies become friends. Evil becomes good and good becomes evil.
It's possible for a symbol to change in representation of what it's referencing.