Khalistan movement was suppressed with an Iron fist.
From 1984 until 1992, India deployed 500,000 Army troops in Punjab. All Public gatherings of farmer unions were banned. That is how India managed to JUST retain Punjab.
Shameful capitulation cannot prevent Khalistan 2.0.

Regarding the role of Indira:
It is true that Indira really took very strong decisions against Khalistanis from May 1984 onwards.
It is also true that she did very little until then. She also indulged in the same appeasement politics which gave strength to Khalistan movement.

There is no comparison between Indira and Modi. They were from different eras and faced different challenges.
However, when it comes to Punjab, Indira's history has a lesson. The lesson is that Indira's appeasement did not work, and it only aggravated the situation