Is the conscience reliable?

“A person’s moral sense of right and wrong, viewed as acting as a guide to one’s behavior” — the dictionary definition of “conscience.”

Whenever I make the common-sense argument that people need to hold themselves accountable to a morality-giving, morality-judging God — specifically, the God of the Bible, and more specifically, the God of the Ten Commandments — a flood of incredulous, frequently mocking, responses immediately appears in the comments section and on atheist and left-wing websites.

Is God Morally Unnecessary?
The gist of the God-is-morally-unnecessary argument is this:

“Unlike Prager and other religious people, I don’t need God to tell me murder is wrong. My conscience tells me that. I don’t need to answer to any god; I answer to my conscience.”