First, you should try the setAliasTexParameters() method in CCTexture2D.
I don't think there is a global way to disable anti-aliasing (I'm almost certain it's on by default), but you could probably modify CCTexture2d or CCTextureCache so that all your textures are aliased by default.
For the CCLabelBMFont, you want to check that there is only a 1 bit alpha channel (or put in another term, the transparency must be either 0 or 100%, not anything in-between) in your spritesheet.
Last, try to see if there are some OpenGL global functions that work better. A good place to try them is in CCDirector::setGLDefaultValues.