Smart investors would take profits and wait for such dumps to buy back and fill their bags again.
People should always understand one thing when the price of Bitcoin start increasing automatically it will effect on the altcoin prices. So we need to wait and see how the market is moving towards a positive direction once the price of Bitcoin increased little in the market. Instead of selling them for the short term it is better to hold them for the long term until your desired target is achieved.
It's simple, people has to understand this:
BTC rising, ALTS falling on BTC pair, and possibly rising on USD pair
BTC consolidating, ALTS rising on all pairs
BTC fallin, ALTS falling on all pairs
So, all you need is a very good luck and solid nerves