Dont suggest to put all his capital in one coin that is too risky, ethereum is good but we all know that this time market are facing dumping of coin value. Much better to have multiple coin to have many option what ever happens your capital will not lost easily.
But if the suggest is for trusted altcoin like ethereum, then the risk that coin will be scam is small. I think many people will have no doubt about that. It doesn't matter if the market is in bad condition, as long as those who buy can hold the coin, they will get the benefit later.