I doubt that there is any reasonable way to do this. The inode is a mount point, so the unlink system call can't touch it. I would just rename to "..." and leave it alone. It isn't causing much trouble. It's like a bullet too close to a spine...it's too risky to attempt removal.

One thing that might work would be to try nfs. Export or share the root volume. And then use nfs to "remotely" mount a second copy of it. Then try the unlink via nfs. This really should fail, but with nfs, you never know.

And the final option would be editing the raw device. You may have a program called fsdb for this purpose.