I have minor issues with his methodology and definitions. Nevertheless, his conclusions are reasonably valid. Though rather than saying that there's an inverse relationship (negative correlation) between analyst rating and actual future performance, I'd be more inclined as to describe the relationship as none or random.
M* says that "The Analyst Rating is based on the analyst's conviction in the fund's ability to outperform its peer group and/or relevant benchmark on a risk-adjusted basis over the long term."
The author looked at raw performance, not risk-adjusted performance. So that's one issue. Another is related to the definition of analyst ratings. Obviously M* isn't really looking at a fund's ability to outperform its relevant benchmark. Else how could it give VFINX a gold rating, when with near certainty it will underpeform its relevant benchmark over any time period? M* is really rating funds against their peers.
With that in mind, a better (or at least different) analysis would be to look at the percentage of gold, silver, bronze, neutral, and negative funds that outperformed their peers over his selected five year period (1/1/2012 - 12/31/2016). Using this metric, the results are virtually independent of rating.
6/27 (22%) of large cap gold funds failed to beat their category peer average. (Two additional funds were merged out of existence: Vanguard Tax-Managed G&I, and Morgan Stanley Focus Growth).
3/1
5 (20%) of large cap silver funds failed to beat their peer average.
3/11 (27%) of large cap bronze funds failed to beat their peer average.
No neutral funds (out of 11 survivors) failed to beat their peers, though Columbia Value and Restructuring (UMBIX) and Putnam Voyager (PVOYX) were merged away.
The author reviews only one of the two negatively rated funds. I assume that's APGAX. Aside from a grouping of just one fund not being meaningful, this fund changed management almost immediately (Feb 2012). Curiously, M* still refuses to rate this now five star fund above neutral, because it says that five years history isn't long enough. The other negatively rated fund, the one I think the author disregarded, is LMGTX. This one also changed in 2012, even more significantly. It changed from being classified domestic to being classified foreign.
Another problem with the analysis is that because of the funds M* selected, there is a tendency to double count. It's as if M* gave medals in 1998, and awarded gold to half a dozen Janus funds, all virtual copies of each other.
That's what happened with at least a couple of families: Yacktman (where gold Yacktman and silver Focused both underperformed), and Weitz (silver Value and gold Partners Value both underperformed).
Overall, I think the best (worst?) you can say is that the analyst ratings are a better indication of which funds are popular (M* doesn't pay much attention to lesser-followed funds) than they are any indication of how funds will perform.