That's a very intelligent point, but let's think specifically of BTC's utility as a store of value. A comparable alternative may be gold, and it would be fair

That's a very intelligent point, but let's think specifically of BTC's utility as a store of value. A comparable alternative may be gold, and it would be fair to say that the gold market could be heavily impacted by a few large holders who choose to sell their holdings. However, those holders tend to be governments. Many of the top holders are fairly representative governments, so initialization of a mass gold dumping is less likely than if they were individuals or small corporate entities, I think. They would be throwing away value that belongs to a large group of citizens, and there would be trade ramifications because their trading partners would take it in the face on their own reserves. The real reason many people don't initiate aggressive sales is that, barring a mass exodus from a collapsing financial instrument where the price is going to drop anyway, nobody wants to hurt their own mark-to-market by pushing down the prices. The only exception to this would be a fire sale where there is a mandate to liquidate a holding in order to return value to creditors. Not only that, but price impact is often reversed by other, later trading. So even if your intention is to put selling pressure on the instrument, it may not have a very lasting impact on the price. However, if you assume everyone else will follow suit and race to the bottom, then there's a definite first mover advantage. That's almost certainly not the case for precious metals, and generally not the case for currencies issued by stable and relatively uncorrupt governments, but it may be the case for BTC because it is new, volatile, and unsecured/unbacked.