Even though we know the shia rijaal system is a total mish mash, an examination of the chains of the reports would really help. As the shia could turn around & say they are weak reports.
To provide reports whose chains contain narrators who are accepted by the shia would leave them conered to just use the taqiyya ploy, which is easy to refute. Easy because:
Most reports of Jafar Saddiq cursing or denouncing Zurarah contain incidents where Zurarah has been propogating his beliefs in kufa & the people who hear this come to Jafar Saddiq to tell him what Zurarah has been saying. Then Jafar in reply curses or condems Zurarah.
How can this be taqiyyah? Its illogical. Jafar is not protecting Zurarah here as the latter is openly propogating his heresy & Jafar when told about it then curses him. If anything it would endanger Zurarah rather than protect him.
It seems that not only was Zurarah openly cursed by Jafar, he openly opposed Jafar too.
In Kashshi's Rijaal:
Zurarah is reported to say: "may God have mercy on Abu Jafar (mohammed al baqir)! But as for Jafar, my heart has turned away from him". When he was further questioned, Zurarah claimed that he had turned away from the Imam because he had revealed his defects.
Also in the same work of Kashshi:
When Jafar cursed Zurarah & the latter was told about this, he (Zurarah) said: "this companion of yours (meaning Jafar) does not have insight into the words of intelligenr men".
Abd Allah Mamaqani (prominent shia scholar who died in 1932) himself in his work 'tanqih al-maqal' acknowledges that there are too many reports of the Imams cursing Zurarah, so al khoi's (recent shia scholar) assertions that the chains are weak are not convincing. So Mamaqani puts the reports down to taqiyyah. Note al khoi does ackowledge at least one report which has an authentic chain with Zurarah being cursed.
Again in Rijaal of Kashshi, Zurarah seems to favour qiyas when ibn Miskan asked him: "is this according to your view or based on a narration?". Zurarah replied: "is not independent reasoning better than the traditions?".
Add to this that Zurarah didn't even know who the Imam after Jafar Saddiq was. Its reported in kashshi's rijaal that Zurarah sent his son to investigate who the Imam was after the death of Jafar. Zurarah died before his son could return to tell him! Both Muhsin Amin in Ayan al shiah & Abu Ghalib az-zurari in tareekg aal zurara confirm this report to be saheeh.
How could a man who claims to be so close to the 5th & 6th Imams not know who the successor was? Especially as both Zurarah & Musa Khadhim were alive for at least 2 years after the death of Jafar (thats when Zurarah died).