Except that spoof only works if you have a valid ID to work from, if there's no way to analyze something to get a valid ID then basically it's a closed system. And closed systems are bad from a gameplay standpoint.
Well, I agree. Just a debate about RAW, or at least consequences of various interpretations.
However, thinking about it, this is the way to make it completely abusable:
It's been established that banning an access ID from a system is insufficient in and of itself to remove the user's _current_ subscription from the system. You have to terminate connection, or do some admin-y stuff to remove them from the subscription list.
So, consider the following scenario:
(i) Take over a node
(ii) Disarm or disable any offensive IC
(iii) Terminate connection of any spiders
(iv) Apply policy of "_no_ access IDs allowed to connect to node"
(v) Remain on node like a hacker pimp.
At this point, if it were the case that Hacking on the Fly could not circumvent the access ID ban, then you would have an unhackable node, which is definitely not something we ever want.