At no point did I suggest that anyone should put all their money in to bitcoin. What I said was that spreading the money you allocate to cryptocurrency among different coins is not diversifying your portfolio.

That article you linked agrees with what I'm saying. It says "Portfolio diversification is the process of investing your money in different asset classes". Altcoins are not a different asset class. They are all cryptocurrencies and they all follow bitcoin, so do nothing to protect your portfolio against a bitcoin bear market.

If you want to buy altcoins to chase some pump and dump profits, then by all means go ahead, but that isn't diversifying - that is gambling. Diversifying your portfolio means investing in different asset classes - stocks, bonds, commodities, real estate, etc.