Those are all legitimate questions. You said your friend listened carefully at first and was sceptical. Sounds reasonable. Your friends shouldn't just listen to you.
And you should be sorry for your shut the hell up expression (I see you've edited this out now). You started the conversation having already put a lot of time and thought into it, and that was the first time they had heard about it and wanted to push the logic of your argument.
Considering Steemit is being advertised as "Blog. Get Paid" (even billboards saying this now) and it is unlikely this will happen to them, your friend sounds intelligent.