1. Assumption: Morals are objective. Then we must ask: Who decided on them? We can instantly discard any God,* and there has been no account of a force of nature that would be able to define what is moral/immoral either, thus it is safe to assume that no objective morals exist.
2. Assumption: Morals are subjective. This would mean that everyone decides what is right and wrong on their own, which in turn means that the words "moral" and "immoral" lose all their meaning. What a person simply expresses by claiming that something is immoral is that they experience a negative emotion from it. Instead of claiming that X is immoral, claiming one dislikes X serves the exact same purpose. With morals being completely meaningless, they might as well not exist.
To quote the one and only great MichaelBurge:
Your move.when you say, "Murder is wrong" - it's stated like a fact but if I actually try to tease apart what it means, I interpret it like "I dislike murder with a strong negative emotion; do so too" with a weak imperative on the second part
*Any God described and believed in today cannot logically exist because the descriptions of them simply don't meet reality. Earth = 6000 years? Nope -> claims don't match reality = That definition of a God doesn't exist. I don't want Wingflier or anyone else to hijack this thread into a religion discussion, so if anyone starts posting about religions stuff, please just ignore them. If anyone wants a discussion about religion, you can find two recent threads about it here and here. (2nd is locked, but you can probably just read through it and pretend you're arguing)