Oxford are not on the radar for many Cobblers but the as you are just down/up the A43 the extra away support is bound to generate a some sort of rivalry, mainly with those that travel to away games.
I dont know what forum you are reading but your match thread on THE is mostly reminiscing about general old away games and I guess that's to fill the void. No-one really hates Ox fans, there's not much to hate as you are such a pleasant set and as you say, not feeling anything.