Of course there's a goddess of fanatics! Two of 'em:
Juvenal uses fanaticus in Satire 4 with reference to Bellona and in the 2nd (along with Livy) with regards to the priests of Cybele. The word is actually pretty rare - Perseus should only 18 instances, mostly in Livy and those mostly refer to the galli.
Bellona was a peculiarly Roman goddess of war. The sister (or wife or daughter) of Mars, her temple is where the senate would convene to meet with persons who could not enter the city, e.g. commanders still holding imperium. Her priests, in a Spring festival, would dance and stab themselves in the arms and shoulders with knives.
The galli, priests of Cybele, as is well known, would castrate themselves (presumably only once) in an ecstatic celebration on March 24th. Roman citizens were prohibited from joining this cult until the time of Claudius.
There is no classical deity of "politics" in the modern sense of the word(s). However... The personification Harmonia (which means just what it looks like it means) did something like that for the Athenians. She originally hung out with Aphrodite and the verb form of her name meant "to become engaged" and in the middle voice "to marry". By the 6th C BCE, she's mixed up with "eunomia" and pertains to stability in the polis.
At Rome there were several temples of Concordia who personified orderly relations between the plebeian and patrician classes. The largest (set against the base of the Capitoline hill at the NW end of the Forum) wes built by Camillus in the mid-4th C. BCE and restored several times over the centuries. Ultimately Tiberius re-dedicated it to "Concordia Augusta".
In re-reading that post you could say the classical definition of a fanatic is someone who:
1) runs around in circles while
2) gesticulating wildly and
4) shouting nonsense and then
4) falls down and hurts himself
I don't know if the two no. 4s was a typo or not. But I hope it was intentional, because it's perfect that way.