Breaking the law is often considered immoral, depending on the person.
> copyright law is an artificial construct
Any human-made rule is artificial, any form of order in a society is artificial. Copyright laws are just on a very high level, compared to other rules.
> copyright law is not a reflection of natural, fundamental morality regarding the sharing of ideas and creative works.
There is nothing natural in creativity. It's all in your mind. There is also nothing natural about ownership, it's just rules that any higher society at some point considers as necessary.
> In conclusion, when I personally say "copying is not theft", I'm simply saying, let's not conflate the issues, so we can have a more nuanced discussion.
There is no nuanced discussion about this. Theft and stealing are legal terms. If you break the laws, they apply. If they not apply, you have not broken the law. The nuanced discussion is only about the laws themselves, whether they should exist and in which form and details. But this discussion is usually about whether people are willing to accept the foundation of society itself or not. In which case you could debate "nuanced" about any law.