Everyone has his own opinion on this, I think that every person uses risk management and there is nothing wrong with that! Everyone has their own goals, someone invests for a long time, who has the goal to earn as quickly as possible, so if he sells bitcoin for further reinvestment, it will only be better and more profitable!
Definitely everyone has an opinion on this matter and we all make decisions that we think are right at some point. Sometimes you need to sell just because you need cash although you know that that's not the perfect time for selling.
I don't think that generally selling bitcoins is a stupid thing to do. After all selling bitcoins is an important thing for the said cryptocurrency as it promotes the pump and dump function into the system. I'd say that selling is a matter of timing. And if you don't sell at the most optimal times to sell, then you're up for a very big loss coming to you.