Actually Before I comment on HODL or no HODL, I need to say it depends how you purchased the coin and at what price.
Suppose I purchase something at $100, it means I am confident on my research that its price is $100, if now market start trading at 90$ and my research still says it is good at $100, then I will HOLD. If I now come to some new facts that make me believe that it actual price $80. then I will sell at $90 at once.
Yes I agree with you because if someone buy some coins from any exchange they want to have a good profit on it, right? so they need to buy in low price and sell it when they think that they can have a good profit on it by just selling their coins, so if the price cannot make a good profit for them is better to hold their coins and wait the right time t sell it.