I know this because I happen to be somewhere where someone that was there that day and for the shoot is. And this person isn't a publicist, nor are they invested in Bale's career. They're just someone that thinks it is absolute bullshit that this moment in Bale's life is being aired and that the real story should get out there.
The DP on TERMINATOR SALVATION, Shane Hurlbut, is a apparently a light tweaker. He's a fairly young DP and likes to fiddle with his lights on set during action, which is a big "NO NO" on most productions unless worked out in advance with performers. But apparently Shane was a pretty unrepentant light tweaker.
The scene in question, was a very emotional and tough scene between Christian Bale and Bryce Howard. A scene that required soul bearing and a deep level of immersive concentration. The sort of scene where everyone on set knows not to get in anyone's eye lines, and definitely not to move lights around while FILMING. You lock that shit down before the scene starts.
Bale had indeed warned the DP on multiple occasions about messing with lights while the cameras were rolling, and Bale was in the midst of a painful scene with Bryce, what was described to me as being the emotional center of the film and his character for the film.
Now, the reason I know all of this is because the person that was there, felt that it should be made perfectly clear that Christian Bale was the utmost gentleman and cool guy on set. And the DP really was doing something that professional DPs with experience just don't do. Not during a performance.