Victorian Morality and Choice

If a person thinks cross burning is immoral, he or she should not burn crosses. If a person thinks the genocide against Christians in Darfur is wrong , they should refrain from this killing. Who has the right to say that others cannot do acts just because he or she believes they are immoral? What does "immoral" mean anyway? It was wrong to impose abolition of slavery on southern states, based on judgemental ideas of right and wrong.