While there are some signs of slowing inflation, there are still lots of worrying signs as well. His argument about wages is wrong. The Fed is not trying to reduce real wages, which is what we actually care about. Current nominal wage growth—which is just over 6%—is in large part driven by expectations of inflation that is well above target. Paul Krugman has basically made this point here—no wages are not the main cause of higher inflation, but we're never going to get inflation back to 2% with wages growing at 6+ percent. That does not mean that workers have to get poorer, because we're talking about nominal wages, not real wages. If we get inflation down, real wage growth can actually be higher than it is right now. The goal is to get inflation back to ~2%, and then wages growing at 3-4%.
Siegel said that when you replace lagged components of the CPI report with on-the-ground rental prices and housing prices, inflation is actually negative, not positive.
First of all, the Federal Reserve doesn't even use CPI, they use PCE. You would think someone criticizing the Fed would at least refer to the correct price index.
I would like to actually see this data, but I highly doubt this is true for any significant period of time (my guess is Siegel is just referring to one month or something). The inflation currently is quite broad-based, it is not concentrated only in housing. That's one of the more worrying signs. Even slow price growth in housing over the medium-term won't bring inflation back to target unless other categories cool as well.
“There’s tremendous evidence of slowing inflation,”
And yet, it is still expected to remain elevated for some time. Professional forecasters still expect PCE inflation to remain above target all through-out 2023. Markets broadly seem to expect the same.
If the Fed eases up too early, they risk high inflation becoming entrenched, at which point it will be all the more difficult to bring down. They aren't going to ease off until there is a much clearer trend than there is today. The signs that Siegel is pointing towards are just too inconsistent to justify stopping rate hikes.