Dude i just asked you define me how to detect "Fake dethreating" Vs Legit, THAT way that computer can calculate it using algorithms and such.
The blatants are easy. The ones who repeatedly get a single kill in a match before driving to the other side of the map and doing nothing. The players who un-equip or holster their weapons and just feed the enemy. The players who openly discuss dethreating in chat. Those are cases that even GMs could easily handle, and as Lixil said report so they can recieve their temporary bans.
As far as the more sublte cases thats what Fairfight is for. Data collection. Players who perform at one level either while silver or while in bronze district, but show a completely different level of ability once they reach gold or find themselves in a silver district. Im not sure if you think that is beyond the scope of possibility or not... but it certainly is not.
Dethreating has done more damage to APB than even cheating. G1 of old did nothing about it and look where we are. Im not sure why anyone would want this to continue, or would defend the game owners who are doing nothing, absolutely nothing, about it.