There were some great posts in this thread, but let us speak logically...
If we are to have true good, there must be an opposite, let us call it evil for the sake of discussion. Preschoolers might call it "bad."
That leads to thinking about the contrapositive: If there is no evil, there can be no good.
If one will not acknowledge evil, they will eventually fall to either anarchy or an attempt to enforce an artificial definition of acceptability.
Some things are just cultural perspective. A lot of us today would have considered the Mayans "evil" because they performed human sacrifices, but they didn't think of it as evil.
Logically there either is, or is not good. If one denies evil, how can anyone condemn anything that anyone does?
I do not know how the Mayans selected their sacrifices.
People purposely killing people for no fault is evil.
I have already stated where this ends; which do you favor, Anarchy or Control?