If you want to diversify, you must choose non-correlated assets. Non-correlated coins do exist. Just look at the article's 2017 chart. BCH was not correlated with BTC, so diversifying into BCH was a good choice. This year, however, you will need to find other coins.
i disagree.
altcoins in the long run, they all act the same meaning they go down whenever bitcoin is active. and BCH has not been an exception to this rule either. the difference is that BCH has been new, controversial and advertised to death in the short time it existed so it might have acted a little differently from other altcoins.
but for instance when bitcoin drop began in December, BCH drop also started with a little delay since it was on a pumping spree with also a delay but the drop happened with the same process.
of course in short term (less than a couple of days) there is always exceptions because pumps happen.
Even more recently, with the bitcoin rises, not all the altcoins were jumping along as well. There's definitely a difference between the coins, but I think there's some truth to the statement that "the movement of bitcoin often influences the movement of altcoins as well."
To back this up, there isn't really much more to look at than graphs. Take a look at coinmarketcap (
https://coinmarketcap.com/). You'll notice that a lot of the trends are pretty much the same as Bitcoin, aside from a select handful. Taking a look back at the extreme bullish run and the aftermath in December 2017, you'll notice there's pretty much the same trend. I'm not sure if you can group all altcoins together. I agree that they're all competing against Bitcoin, but they're also competing amongst themselves for the most support from the community.