People will buy where the money is made. Things like this will always happen throughout the altcoin market right now. Id look at this as a primal-esque problem until altcoins become more stable and the best apples are the only ones left hanging on in the market. Survival of the fittest. Let people take their profit because the market will correct itself in the long run 
well that's right the last one who can hang and continue growing together with btc will make its value in the long run, as we knew thatpeople really using alts just to continue getting profits and the cycle will like this as long as there's no real means for the alts unlike btc.
Yes, I agree that people should not buy the overpriced altcoins in the market. Even if you missed the boat, I rather you wait for a deep market correction or look for opportunities elsewhere.
There are always opportunities in the altcoin market. Buying into those heavily pumped coin is risky and encourages pumper to pump and dump other coins which makes newbies leave the market after getting burned.