The price didn't drop particularly low, IMO, but those who think it will fall down even more and who aren't willing to wait for lots of months or perhaps over a year for Bitcoin to go on a bull run are reasonable in the desire to cash out now. I don't care about the price as much and try to be more flexible, but I don't judge those who choose to sell, and we can't convince people not to do it, since we can't guarantee that Bitcoin will be up soon.
As long as this is the result of a strategy which has been thoroughly tested then there is nothing wrong with selling at the moment, however if someone is selling their coins out of panic then this is a completely different scenario, because as you state the drop we are experimenting is of only 10%, and while in other markets such a drop could be disastrous, on this market this is relatively common, and anyone that panics over such a movement probably is not ready to be invested on this market anyway.