As a private pilot as well as having a 107 certificate, I can tell you without question that trying to find traffic below you that’s mixed in with ground clutter even after having its direction and altitude provided by ATC, can be very difficult. A drone would be quite a find. Given there are a few smaller airports along the left side of the standard instrument approach for LAX, and the photo looks more like a white blob with the photographers own description of a flashing light, which could be that of the rotating beacon of Chino or Riverside airports. A lot of haze, with low light makes my possible explanation questionable as I can’t make out an airport near the light source. Another possibility is the rotating beacon and/or strobe of another aircraft. If it was flying a perpendicular path, it might appear to be stationary to this guy.
Also, the description of “some sort of a Phantom” suggests he is only aware of that model, since the basic design hasn’t changed since inception, and he’s just trying to make himself more believable with a positive ID. Would have been more believable if he didn’t try to lay it on that thick. 99.9% this is a misidentified object with a side dish of overactive imagination, or malicious political agenda.