If a bad actor wants to imbed 100kb blob of illicit data they can go straight to a miner. In this case the blame will be put on the miner and the bad actor for voluntarily putting this illicit data on chain forever. If a bad actor can get a 100kb blob of illicit data imbedded anonymously using other people’s nodes (the p2p network) suddenly the blame will be put on the bitcoin network for supporting and facilitating this activity as a feature. You’ve got to remember op_return is a native feature of bitcoin and so by opening up the data carrier size to 100kb you are saying “hey this is a legitimate and supported use case for bitcoin”. There’s a blinding difference between the two…