I mentioned above that I do not know the legalities. I do believe it is lawful to quote and attribute small passages of another's published work, but mostly I am guessing.
In the case which we're discussing, we're not talking about a passage in a larger work, we're talking about the entire value of information in question. It's a message at a paid site, not a book; the business owner's work, therefore its value, is within that relatively short post. To post that information elsewhere is to deprive that author of his entire work, which might have been ongoing over months.
If someone wants to post that information here, let him or her put in the work to first find that information rather than take it from there and post it here.
Don't know the legalities. But, in my humble opinion, yes, it is unethical to post that information here.
PS - Another question. Why would someone, who reads that information on a paid site, be motivated to scurry over here to post it? Is it not enough to possess the information for which you paid at that site? Is it merely ego that causes someone to race over here and post it, as if to say, "Ah-ha, look at what I know!"