Really? I thought he was famous for calling the tech market collapse:
His profile on the sources I looked at said he was criticized for staying bullish too long. Even the source you quoted refers to him as, "professor of the bull market."
If anyone is famous for calling the tech market collapse I would say it would be Shiller. He had been saying it for awhile, and even wrote a very well known book about it, "Irrational Exuberance," prior to the crash.
He's telling people that stocks will do better over the long run.
No. He said bonds are "very dangerous." That is very different than just saying one asset will do better over time.
Would you care to share your AA?
For retirement: 100% stocks right now. When I get closer to retirement I will add bonds. I will hold bonds just before retirement, and in early retirement. This is because bonds help you weather sequence of return risk in those early years. Long term I probably won't keep very much in bonds. That is ME. I have a very high risk tolerance and I fully understand the implications of that.
In my HSA: enough to cover the deductible in cash, enough to cover the max out of pocket in bonds, and the rest in stocks.
Most people don't have that high of a risk tolerance. Investing isn't like engineering. It isn't 100% logic. It is a mix of logic and emotion. The most logical portfolio isn't the ideal portfolio for everyone. If someone invests in something that is too aggressive they may make bad impulse decisions in a crash. Understanding your own internal feelings about this is one of the most important aspects of investing.
I would also like to point out historically 100% stocks has averaged 10% returns, but a 70/30 has averaged about 9%. The difference in a crash is remarkable. With rebalancing the 70/30 will normally recover faster than a 100% stock portfolio. It isn't as big of a return difference as many people think, but it is a big difference in volatility. To piggy back off Kaspian, the reason the returns are so similar = benefits of rebalancing.
Conclusion: if someone is more comfortable with 70/30 they should be 70/30 and stick to it. If there is any risk they might panic, or even experience undue stress in a crash, then they should probably stick with the more conservative portfolio. Giving up a 1% difference in returns to have peace of mind and less stress is any easy decision for many investors.