I'm sure I'm feeding a troll now, your post seems intent on twisting things around in order to make your convoluted point.
The whole "under 1024 is safe" is generally regarded for connecting *to* ports under 1024, not receiving connections from them. Yes, some services (NFS in particular) want to trust incoming connections from 1024 but they're in the minority. The most common case is trusting a service listening on ports less than 1024 as being set up by the admin and not some random user. But you knew this.
You also know that if you've got admin access, you *are* root. This also is not news, but you seem to feel that I'm concerned that you can sudo from your own system and make it look like you're trustworthy on my network. If I was so inclined as to trust port numbers alone (and for the record, I don't trust incoming port numbers at all), you can bet I'd also be whitelisting IPs and MACs at the switch level (i.e. locking MACs to physical switch ports) and have alerting whenever a non-sanctioned connection was made.
That would be, however, a very special network topology and not something I'd personally admin. Nice straw man, though.