i don't hold any of them in first place to want to decide what to do when they get dumped! we all know that sooner or later all the altcoins out there are going to get dumped so the only question is when to get in and how long to stay in.
the answer depends on the market itself and the potential of the ongoing pumps that the specific token has. then as soon as that pump ended you must make your exit instead of waiting around.
Holding a coin is really for the strong in mind. I just wonder how one will see a coin dumping and wouldn't want to sell and take out capital at least. I guess that's for a longterm hold.. Waiting for the price to rise back to expected price is just a risk