I don't find holding of altcoins to be dangerous, because among the entire altcoins listed on coinmarketcap very few grew while bitcoin was declining in value. But now as the price of bitcoin has started to increase, most of the altcoins too started to increase. This confirms profit on holding of altcoins.
You have a point my friend.And for me holding alts is not dangerous as long as you choosed the best alts that a big potential to grow.