Selling btc is not considered as stupid decision. It depends on the price and the necessity of the person. If the price of the btc is high, it is possible for the person who have btc to sell what they have. It's up to that person who owns the btc, so I think there's nothing wrong or stupid with it.
Your definitely right that selling bitcoin is not considered as a stupid decision because it depends on the person if he wants to sell it in a low or high price. Selling bitcoin is a risk that is why it is not considered as a stupid decision your just taking risk.