When I shill for a coin (and I do shill for decentralized coins like XMR, LTC or so) then I'll usually provide some hard numbers to back up the claims. So you can do the same thing and your argument becomes stronger
Now to answer your question about undervaluation: this metric seems to be indirectly related with value as a long term indicator for usage (these coins "could" eventually be part of the SOL demand), but not directly, because the value can simply stay inside the stablecoins without ever being converted into SOL. Many users might be simply using stablecoins on Solana due to the lower fees but would never exchange them to SOL.
A possible strategy to answer the question about undervaluation would be to compare the stablecoin trading volume on SOL versus the SOL price evolution. If the growth of this volume is higher than the price increase, then I would say that SOL could be undervalued. The reason is that the stablecoins are actively traded for SOL and thus can indeed form part of the demand, and not only hodled in stablecoins (or used for stablecoin payments).
But as I wrote in the last post Solana has a long way to go to catch up to ETH in terms of market cap, so a long period of positive flows into the ecosystem would be needed.
Another interesting metric would be the value of all (or at least, all relevant, i.e. perhaps the top 50) tokens on ETH compared to those on SOL, including all second layers. If SOL's network value approaches the one of ETH then a "flipping" is possible in the medium/long term.