If the freedom movement came in and dropped $20, 30, even 50 million dollars, it wouldn't make a dent.
Not so sure about this, 20M USD is around 13M HIVE at the current prices, and the biggest stakeholder has around 12. Its delegated, so the biggest HP holder, OCDB has around 8 to 9M HP.
We can argue that it will push the price higher and not be able to accumulate 13M, but if someone is serious about it, he will make the buying gradually in small chunks in a longer period of time, probably a few months. There are always 100k to 200k HIVE orders on Binance at one price level.
Furthermore I would argue that if you want to "fight back" here, you don't need 10M plus HP, a 1M or 2M will do it.... 5M will be more then enough, and you get to those levels in a weeks of buying.
As for the design itself I believe there is always a room for improvement, not sure what that would be yet, one option is always through stake and making tweaks, like having some sort of free protection once in a while... the other would be through decentralized reputation systems (reputation without stake and without KYC) although those are quite complex, not tested enough etc .... we might get there one day :)