If I were in cesc's shoes, it'd feel dirty going to united. He'd be upsetting loads of fans who he's led to believe that he loves Arsenal, he'd be kicking wenger in the teeth, he'd be going to a team which doesn't exactly play the type of football he likes and is best suited to, plus he'd be admitting defeat by leaving barca; acknowledging he failed to achieve what he should have there.
Plus Manchester's a shithole