It's not a good idea to sympathize with terrorists, but how you handle that is what differentiates a matured democracy from an authoritarian shithole and everything in between.
Typically most western countries put people who do this on surveillance, but that's about it. If you start to jail people for thought crimes and what they say you open yourself to being a country that doesn't care too much about human rights.
The problem in India is that this goes far beyond laws - not just political parties but society itself values the emotions and pride (or honor) of a community over an individual. This is partly what makes India a backwards nation.
The demand for freedom for Kashmir is almost about using non-violent means.
This is simply not true. There are lots of Kashmiri Muslims who either want greater autonomy or freedom without any terrorism. India has been unable to engage moderates in Kashmir, and the BJP has tried to throttle the very reasonable farooq and Omar abdullah side of Kashmiri politics just to win elections.
Speech inciting violence is criminalised in India, like it or not.
Yes, India as a society probably isn't ready for total free speech. But this mentality gets misused - as seen with JNU, and with the likes of Mamata Banerjee.
I hope you realise these sedition laws were instituted by the British to try and muzzle Indian freedom fighters:
No sane state would allow something like that to happen.
No, referendums for independence and mostly non violent freedom movements achieved through compromise are extremely common.
Was Kanhaia and Umar Khalid advocating or inciting violence ? Simply sympathising with separatism doesn't necessarily count as actionable sedition. What Burhan Wahni did is - so there is an important distinction here.
The BJP narrative is to club everyone that is opposed to their stance on Kashmir anti national; unless of course they belong to the PDP.