No, he's not helping you; or rather any number of people who are trying to make money on the GTN by selling items for extremely high profit.
The fallacy in your asking to "let us play the market." is that you are implying that you're somehow being prevented from doing so, which simply is not the case. At best you're being prevented from playing the market according to the rules you dictate as opposed to the rules someone else dictates, or a free market.
The simple matter is that people can sell their merchandise at any price they want to. Normally this price will reflect a desire recover production costs, but not necessarily so. If someone is wealthy enough and has the motivation to flood the market with grossly under priced goods, there is nothing you can do about it. They have not broken any rules, stolen anything, committed any acts which are immoral, etc. This is really no different than in real life markets where wealthy parties flood a market with an abundance of money, or cheap goods. The situation will last so long as the resources of the investor persist and their desire to drive down prices exists.
You're upset because now someone else has more control over the market than you do.
Either you find a way to swing the market back in a direction that you can exert more control over, you learn to play by current rules, or you get out of the game all together.