I'm sorry, but that's not even an argument.
Online servers are vastly more stable and secure, and far less prone to glitches and exploits than a system that relies on P2P; a transfer protocol that, I might add, is not difficult to intercept and manipulate; as opposed to being almost impossible with a dedicated server.
Not to mention, P2P relies on a player being the host; which in turn relies on a strong enough computer to handle the load, as well as bandwidth capable of hosting multiple, simultaneous P2P connections; which results in things like; random connection drops, poor networking performance ( notice how SC'ing players sometimes "jump" through space? ), limited user count ( I think it's 32 players per instance at the moment? ).
A dedicated server would eliminate most, if not all, of this when it comes to player to player interactions.
It would also give Frontier the chance to introduce much needed social encouragement features; some players want a "global chat" - something I personally despise, but can appreciate how some would consider it essential.
A dedicated server just makes good sense; technologically, financially, and business-cally.