This article is being paranoid, sure any huge investor with a lot of investment can crash the whole market but will they really join hand to hand to crash the market? As we all know there are more than 1 whale in the ocean and the same being said with this investor. Even if one of them sold their portfolio of ethereum, there is no guarantee that other will follow them or even buying their shares.
Moreover, i think this article already answered their own question,
Most of the whales are not yet traders but ICO’s who hold millions of Ethereum coins which is worth almost billions of dollars. According to some researches almost 3% of Ethereum is in the hands of the ICOs.
Don't think 3% of ICOs who hold ethereum can crash the whole market, if 3% is considered as a pack of whales for all ICOs combined then that doesn't sound like the crash will ever happened anytime
and not to mention if you're talking about cryptocurrencies then bitcoin is included as well and all of us know how much total value of bitcoin compared to other crypto