(...) As for me, the situation you mentioned above will not have a direct effect on the price of Bitcoin as it is the shares of that company that got sold and is not really the Bitcoin being held by the company in question. (...)
Just to clarify, I only meant pure supply/demand market mechanisms, not the psychological effect (such as losing confidence etc).
Let's try to break it down:
So what would happen if such dump caused the price of shares to go below the price of bitcoin (ie. they would be traded below company's market value)? If the arbitrage could be applied, i.e. new shareholders could force the company to sell bitcoins - then all is clear. But if new shareholders could not make the decision to sell, then the only impact on BTC price would be that some potential BTC buyers would choose to buy cheaper company shares instead (so reducing demand for BTC and causing the price to drop).
I can't think of any other factors.