Excessive is knowingly denying someone necessary medical coverage solely for financial gain. If private insurers want to play that game then they can register as a non-profit organization or be an optional layer on top of a public backstop, such as medicare-for-all, an arrangement they've lobbied against for deacdes.

Sadly, they want to retain the ability to deny you coverage for any reason. Their maximum profit happens when they pay out as few claims as possible. The only reason they don't already operate that way is legal enforcement, so let's take that to it's logical conclusion

Where do you think all criminal codes come from? Are they mined out of the earth already written? It's a constantly evolving set of rules based on a society's collective moralities.

There are many crimes today that did not exist 100 years ago and vice versa. Yes, there are crimes that should be punished that are not yet present in the criminal code, and you don't need to be a legal scholar to propose new ones.

I think most people agree deriving financial profit by knowingly denying people necessary medical treatment is immoral.