To not touch politicians would be to take the stand that some people are important politicians and some are not, that would be an inherently political distinction. Thus that route is not apolitical (short of just not moderating at all, that is possible but does not create a platform that people want to use).
I don't know anything about indian politics, or this case apart from what is said in the article. I don't know if this account was banned for apolitical reasons. But to take the position that banning a political party is fundamentally taking sides in a political issue is wrong.
The core question as far as international law is concerned is whether or not Twitter's actions in these instances are those of a state or if it is a private actor. Twitter would say it's a private actor, but considering the close historical coordination between Twitter, the State Department, and the intelligence octopus, one would have to be somewhere between clueless, brain damaged, and a stooge to argue that Twitter is wholly a private actor and completely uncontaminated from American state pressure.
I'm not an Indian, not ethnically Indian, don't care about India, but India should accordingly treat Twitter as if it is an American state actor and seek restitution and remediation under the exact same reasoning that the United States uses to blame the Russian state for election interference among other miscellaneous "cyber" things.
We do use this exact reasoning against the Russians with even less evidence. Our economic policy of attempting to digitally dominate and interfere with foreign powers is also screwing up our diplomacy (not that American diplomacy can really get any more twisted, but still, I'm speaking in terms of the principle here). India's at an inflection point now in its own foreign policy, and it is not helpful to the American interest to have quasi-private frothing algorithmic dogs causing needless diplomatic incidents continuously for no discernable benefit to anyone but Twitter's feckless shareholders.
If I start the "Election Fraud Party", I don't get to complain that enforcing free and fair elections is an attack on me.
And no: I would *not* defend the use of Twitter by the Nazi party if this were the 1930s. In this scenario I would expect Twitter to make an explanation that goes beyond the "violates our terms of service" or some amorphous "community guidelines" nonsense. Twitter is affecting political activity in a foreign nation; I would support India in either banning Twitter from their country or taking civil or criminal actions for silencing political discourse (whatever the local laws permit).