While I'd prefer the coins to not be dumped in one go but instead in increments(as to not dramatically flash crash the market), why should we stop Satoshi? It's his coins, from his own creation. He/she/they have every right to dump every single one of the bitcoins if Satoshi wants to. It's a free and open market.
This of course has always been my position on this topic. Why should I care if he is fed up with hodling? I mean, at a point he is going to want to offload some. In fact, Satoshi will be a fool not to profit from his own invention. Charlie Lee (the Litecoin dude) also did same and sold an appreciable quantity of his hodlings at almost ATH. But the market concern should be that Satoshi doesn't sell off his 1million holding at a go as that will invariably destroy the crypto market with a deep crash.