Just a daft theory on my part, but it's silly enough to be a factor. I've met a fair few Arsenal fans over the years who've genuinely been complimentary about us as a club and fans (met a few arseholes as well!). As well I was told years ago that Jimmy Montgomery and Bob Wilson were pretty good friends and I remember Charlie George being complimentary about us and very down on the mags before the 1998 FA cup final. It's daft enough that in their tiny minds that they don't like Arsenal just because Arsenal have been nice to us in the past, the old "the enemy of my enemy is my friend, the friend of my enemy is my enemy" thing. Knowing how thin skinned most mags are, if Arsenal fans have sung a few Sunderland songs at them to wind them up, they'd definitely take it to heart and react, which would only make Arsenal fans do it more to wind them up. The mags love to dish it out but can't take it when it's dished back at them.
Then if you add in that Arsenal are the kind of club the mags want to be but are no where near that jealousy just boosts it a bit more.
It's a daft theory, I know, but it honestly wouldn't surprise me.