All later Roman historiography is written from the point of view that Nero was a BAD, BAD MAN, AND WE MEAN REALLY BAD. The obvious reason for this is that later historians were writing during later dynasties which had supplanted the Julio-Claudian dynasty, and their legitimacy was, to a certain extent, based on the fact that the Julio-Claudian dynasty's legitimacy had been lost with Nero. Thus, Nero had to be bad -- or later dynasties would be varying degrees of illegitimate.
It's reasonable to consider much of the talk about Nero having killed his mother to be invention or hyperbole, aimed at painting Nero as a villain. Much more credible are the events where some specific transgression witnessed by many people ( for instance, crossing the pomerium at a point that was not a gate, after the great fire) is described.