Thing is, if Bruce was all about preparing for the League turning on the world, he went about it the wrong way. No one but Bruce knew about these plans until Ra's used them on the League. Bruce keeping his plans a secret not only means the League is screwed when something like that happens, but that he acts unilaterally on when these plans should be put into effect. Not to mention, what would have happened if Bruce died and took the knowledge of these plans with him?
What Bruce should have done was have it so every police officer was equipped with a Kryptonite gun or vibra-bullet. He'd have sold the anti Wonder Woman nanites and anti- Aquaman gas for military use. He'd have made sure every single Green Lantern underwent whatever procedure he put on Kyle.
In short, yes Bruce was right that contingencies against the League needed to be taken. He was wrong in trying to police them himself.
Because Bruce, for whatever reason, is the only one who can stop the Joker. He's the one who can catch him, he's the one the Joker can't (or won't) kill. And with his wealth and resources he could easily fix the problems that plague Gotham. Hell, him joining the police force would probably do more to boost moral than anything he's done as Batman.