BVB is because Klopp made them. When he took over, they were nearly bancrupt and dwelling somewhere in mid-table. It was really him and the good cooperation with the management that made BVB the back-to-back league winners and CL finalists of today. Similarly, he took over Mainz when they were in the 2nd division and managed to get them promoted to the first. Inbetween he had the chance to coach Bayern, and chose Dortmund. Now he could have the chance to take over the national team from Löw, but instead just extended his contract. Just proves his intention imo.
Also no way he hates Barca, he has repeatedly talked very fondly of them, especially Messi.