I'll be nice enough to give a response (even if it does suggest I'm a 'Murraytard').
I don't hate DelPo, he generally seems a good guy. I don't hate any player, and furthermore some of the remarks made about players on here are pretty pathetic (I particularly dislike some of the comments aimed at Cilic). But to the point, I thought Ferrer would beat him again because right now, in the here and now, he's a better player. And like many others, I was right. Like certain other players who can be brilliant on their day, in general terms Del Potro is overrated (ridiculously so, by some).
Bitter about what?
Murray isn't just better than DelPo, he's in a higher division and dominates him whenever they meet. Fans of the champ aren't bitter about anything, we're loving these tennis days.
As for the real reason why they're bitter, it's because despite Juan's unfortunate wrist injury/surgery, it took their man 3 years to finally do what Juan had done and win a Slam himself - and even then he did it in circumstances we know, a far cry from Juan's blasting through the two most dominant players of the XXI century. Deep down, they know the truth hence the bitterness
Even though Juan denied Federer a Slam title and Nole an Olympic medal and gave Nadal a good hiding in USO semis, you don't see any particular bitterness from the fanbases of Federer, Nadal or Djokovic, do you? Figures.