I am an atheist and I disagree with many religious people’s opinions. A criticism I face often is that my morality is not objective, and thus my morality isn’t really moral.
I am near-certain most people—regardless of their religion—have the same ethical views as I do when it comes to things like murder and theft; these things are wrong. So objectivity is not a necessity to adopting these ethical principles.
-AD
Reagent Post 
Morality is always subjective. It is influenced by culture, family, friends, media… Even murder can be justified in any number of ways.
I think the way you’re using “objective” would be objectionable, since I’ve seen it used in the sense that it means “applicable to all humanity.” Some Christians would even say it’s universal (because God made it). Since it’s impossible right now to prove a moral value for the entire universe, I would agree with you.
However, an objective value does not have to mean that it is true for all of humanity. “Objective” can also mean “unbiased” or “based on facts.” As the word is used in other circles, it simply means a standard that exists independent of a person’s viewpoint that applies to different people. I’ve argued before on my own blog that secular moral values can be objective (apply to a group of people equally).
Using this reasoning, the moral values against murder (that is, the unjustified premeditated killing of another human being) and theft (the taking of the property of another with the intent to permanently deprive that person of said property) could be objective as it relates to a community, jurisdiction, or even a nation. And I would argue that it would be desirable for secular thinkers to advocate such values as being objective but not being universally objective (like some theists would argue).
If I say Murder is not wrong, am I wrong in some moral way?
That depends on what type of morality you value. I would hope you value one that condemns murder. It makes for a safer society.
I think objective reality is important, it just doesn’t necessarily have to include a god. You can arrive at a rational and coherent set of values and ethics on the basis of reason, it can be based on your subjective understanding of an objective reality, and all of that can be so without a “God” anywhere in that equation. Imo Ayn Rand was spot on when it came to this particular issue of “atheism vs. theistic religion”.