Just for a minute, imagine a world where there is no objective morality. No God or gods, no Great Spirit, no reincarnation, no cosmic consciousness, no universal oneness, no karma, no angels, no demons, no supernatural elements at all. Imagine a world where, because those entities don't exist, they can't be the source of morality, and therefore there is no objective basis for our morality. What would this imaginary world look like?
It'd be a terrible world, for sure.
People, lacking an objective standard on which to base their moral decisions, might feel lost. They would begin to form their own private moral opinions based on their own feelings, gut instincts, and observed consequences of their actions. They might create ad hoc rules based on their experiences and the experience stories of others in their culture. They might sew those ad hoc rules together, resulting in a patchwork moral framework with no consistent basis.
They might take their feelings of joy, love, contentment, safety, and awe to create a concept they call "good". They might take their feelings of fear, hate, insecurity, and revulsion and create a concept called "evil". Of course, because they are based on feelings, experiences, and culture instead of a divine constant, these categories would change considerably over time.
They might notice that bad things happen, and try to figure out why. Some might attribute to unseen forces the good and bad things which (in this imaginary world) more or less happen at random. People, witnessing the deaths of friends and loved ones, and not understanding why or how, might not want to believe that death is the end.
Being sentient, ego-centric, pattern-matching, intentional creatures, people might come to believe that the semi-random happenings are also intentional, and that some kind of intelligence must be in control. Some may come to believe they can exert a small bit of control over their lives by attempting to understand, placate, and communicate with the intelligence.
In this uncertain world, people might find comfort in traditions, rituals, and beliefs: anything which promised certainty. Some might even come to believe their particular ad hoc set of moral rules are not ad hoc at all, but are based on and come from their beliefs. But, starting from different cultures and experiences, we'd end up with hundreds of contradictory theories and moral systems, all competing with each other, sometimes peacefully, sometimes violently.
Without an objective and divine morality, some people might steal, rape, murder, start wars, or be bigoted, and other times some might be helpful, kind, compassionate, creative, and loving. They might believe in things that are not true, and some might search for truths and certainties which simply don't exist.
And finally, although people could try to judge which ad hoc system of morals has real-world consequences they like best, there'd be no way to say that one person's morality was more correct than another's.
In short, a world without objective morality would be an uncertain world, where terrible and wonderful things can happen, oftentimes for no good reason, where people believe many different and contradictory things, and where we must choose for ourselves what constitutes good and evil and how to act towards other people.
I, for one, am extremely glad the world we live in bears no resemblance to such an unstable, uncertain existence.