This was the first and most widespread form of religious persecution in the ancient world until the Christians came on the scene, and it wasn't until Julius Caesar repealed the tyrannical legislation that they were free to worship their god openly once more. Of course even during that time Bacchic and Dionysiac cults were plentiful in Italy and Rome, as we can see from things like the records of cult associations, the Villa of the Mysteries at Pompeii, the preponderance of funerary and symposiatic art reflecting his motifs, and the abundance of literary and poetic references to him. They just had to get permission from the Senate and maintain a polite and civilized façade. Caesar's repeal of the legislation merely ended the appearance and pretense of illicitness surrounding these cults, which nevertheless earns him a special place in my affections.
But really if one has any doubt concerning the identity of Bacchus and Dionysos they need only consult the Latin poets and historians of that period, all of whom were quite certain that they were dealing with the same god—and who are we to argue with them? Or go a little further back and you'll find Sophokles praising Dionysos as the "Lord of all Italy" and Plato talking about the famous Dionysian festivals celebrated in Magna Graecia. His cult flourished especially in the Apulian countryside, Southern Italy, and Sicily, which is interesting because those regions are exactly where you find Tarantism and related ecstatic cults nearly a thousand years after the fall of the Western Roman Empire, with only a thin and transparently artificial Christian veneer on them.Clearly once he was established there the roots of this god have run deep in the Italian soil and consciousness.
Sannion, thank you so much for taking the time to answer my questions. It has been a true pleasure. For more information on Sannion and his work, please check out his website at http://thehouseofvines.com.