MM's have nothing to do with it. If you offer your shares at their bid, they have to buy them. If you buy at their offer, they have to sell them to you. They set their spread, and TRADERS decide what to do. So, it is TRADERS that affect the price, not MM's.
If you sell at market, the price will dive, because you are saying you will take whatever MM's will give you for them, and their offer goes down immediately.
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