I'm glad you shared this but for now anyways, I'm going to agree with the part where you said essentially "anybody can post anything and the market determines the value..".
I want scams exposed, and I think you gave enough info for a regular user here to figure out whom you're referring to (without naming names), and if I'm right about who he/she, then I'd say he/she is free to post those opinions and time will tell. But I'm reminded of the msgivings fiasco. Scams may prosper here for a bit, but they'll be found out and downvoted/flagged/exposed - hopefully. But if you're not going to name names that just makes it harder actually. I know nothing of that person's background tho, and can't judge without more info/facts. I probably won't judge anyways.
As for me, I just bought $200 worth of BTC via Coinbase that I'm waiting to clear, so I can invest in Steempower. Obviously, I'm not ready to quit, and am vesting/investing in the long term power of this community.