It is ridiculous to claim any kind of authority to regulate what people can and cannot do. Especially when you are in absolutely no way elected, and in no way accountable for your decisions. People who regulate others' actions who are neither elected nor accountable are generally described as "dictators".
Due to the nature of the trust system here, I don't think that comparing it in any way to a traditional election/dictatorship is valid.
If you were to hack my account, and it was not possible to sell my account, you could scam someone with my account, which IMO is worse than you selling my account because if you sold my account, I could argue to the buyer their lack of a signed message is an indication they did not do proper due diligence and they were scammed by someone else, however if you were scamming from my account directly that argument would not work.
There being multiple ways to scam with an account doesn't invalidate that account selling opens up another method to do so. I'm not entirely sure what the argument is here.