It is rather a question of how much of what we know about his principate is coined negatively by our sources.
After the principate has been established, the senators lost the greatest part of their political power as the senate itself became more or less powerless against the institutionally strong position of the emperor. Furthermore the nobility misses its struggle for public offices because the cursus honorum that determinated a senator's ambitions in republican times faded increasingly to a state of insignificance.
Emperors that appear as "good" ones in our sources, are those who did not point out how mighty they were and how much they stood above everybody else. Augustus for instance struggled his entire life as princeps with keeping the illusion of the restored republic ("res publica restituta") in which he just served to defend it (with shining success). In his extremely effective propaganda he did not take any offices nor any honours, he was officially given these by the senate.
Frustrated senators who still wanted to profile themselfes, searched for other fields of competition and found one very important in producing different styles of art and literature - one of them (one of the most important too) is writing historiographic texts that are mainly our sources for political history in the principate's epoch in Roman history. To cut a long story short: "Bad" principes always failed in keeping the illusion of balanced power relations. Nero for example declared himself winner of artistic competitions in Greece before anyone even started to play. His disinterest in political affairs and his concentration on his beeing as an artist without any real concurrence simply has to be seen as a scandal for the nobility.
Nevertheless we hear positive voices of Nero's rule: He was seen as an fair judge and especially his close relation to Seneca was seen positively. Later in his principate (when he breaks apart from Seneca too) this changes and the negative image coins Nero's reception until now.
Another point you might think about is the topos of the crazy emperor burning down Rome and chasing Christians. Both is historically at least strongly discussed. The fire was much rather an accident and the persecution of Christians is most commonly seen as a result of searching a scapegoat. Tendencies against Christianity existed and were by no means brought up by Nero himself.