My father was from a generation that did support each of the local clubs. My dad before he died told me of the days when he would go to Roker park one week and St James the next. He even admitted to going to Ayresome park on the odd occasion.
I am sure there must have been rivalry back then but not to the degree it is now.
I am a sunderland supporter through and through but I have no real hatred towards the Mags. Whether I really want them to do well I am not sure but I suspect that is jealousy as opposed to hatred.
I would be delighted if they were premier league runners up as long as we won the league.
Could I ever support them. I would find it hard but over time probably yes as I would rather be loyal to my NE roots than support a NW or SE team.
As for Middlesbrough, well thats a different matter altogether