Yep, there's more than enough liquidity. People clearing more than $70k USD worth of ETH are usually going through OTC channels, not through exchanges like Poloniex and Coinbase. OTC fees are generally higher than exchanges, but offer the advantage of legally guaranteed finality and no chance of slippage affecting your transaction (exactly what happened with GDAX when the price of ETH briefly dropped to $0.10).
When deals are large enough, sometimes they are even executed as a set of "tranches" (large set of smaller transactions over time) so the transfer isn't easily traceable and counter-parties remain largely unknown.
Check out my project, it should solve the problem you mentioned. The goal would be to stabilize the price of Ether on the blockchain so the Ether can be sold off slowly without moving the market.
Its essentially a cryptocurrency risk management system where one user takes on all the profit/loss of cryptocurrencies price change so that other user (fund) pegges their wealth to USD
Well, considering that this amount of ETH was worth double that 2 weeks ago, I don't put much faith in it being worth anywhere near that much if they tried to liquidate it immediately.
So imagine that 6 months ago you decided to get in to the whole crypto currency thing and 'invested' $1,000 in ETH.
Back then the price was ~USD 10.
One month ago, you were pretty happy because the price was ~USD 395, which meant your $1,000 was now worth ~40,000.
Today however, at ~USD 173 your $40,000 is now only worth $17,300, much better than $1,000, but you're not as happy as you were one month ago when the price was only going up.
Then you see the news that this new ICO was hacked and someone's going to be looking to offload $6,000,000 in ETH.
How many speculators in a similar position to what I describe are going to have seen the price drop significantly in the last month, see that someone is also looking to offload a large number of ETH and think "it's been a good run, $17,300 is not bad, time to get out before it all comes crashing down"?
Does ETH have the liquidity to deal with a large number of speculators spooked at losing their 'investment'?