When the price of Bitcoin falls, the value of altcoin also decreases. We can see that Bitcoin is strong in the market and has full control on the market because bitcoin is the king of all altrcoin and all other crypto move with bitcoin prices.
In some time yes it is, when bitcoin dive too deep some altcoins does so but it does not mean that altcoins are price dependent on bitcoin. It is just the reflection of how the trader and investor handle their assets after the king goes down, it is simply securing or cutting the loss. The whole cryptomarket is just the reflection of us, bear in mind that it is zero based.