So if one day you are banned you will find normal and fair to not be able to defend yourself against an "appeal" asking for a permaban? 
If a banned member can't reply to this kind of "appeal", those appeals shouldn't be allowed.
If a banned member can't reply to this kind of "appeal", those appeals shouldn't be allowed.
He can defend himself after his 7-day ban expires or he can defend himself in the thread that he already created. The rule is very clear:
25. If you get banned (temporarily or permanently) and create a new account to continue posting / sending PMs, it's considered ban evasion. The only exception is creating a thread in Meta about your ban.
A banned member is not allowed to reply to anything else, involving them or not, good or bad, doesn't matter. Granted the enforcement of ban evasion has always been a bit of a joke when it comes to most egregious trolls so he might be able to avoid the ban here, but it would be quite ridiculous to add to the already very generous rule by disallowing discussion of banned users just because they can't reply.
You say he could defend himself after his 7 day ban, but the "appeal" could also be made after this 7 day...