Thank you.
You mean there was fear that someone could influence the witnesses to write code which would allow them to freeze someones account?
I think it's imaginable and therefor it's probably possible. But that would require a lot of criminal energy. And people hate being criminals from my point of view.
It is totally totally possible to either nuke or freeze accounts and to move funds arbitrarily between accounts. The key protection against this is the witnesses themselves. That's why it's really important that you choose good witnesses because those witnesses protect you against more or less endless and myriad threats.