Well, other than convincing me that Nijjar might have been an actual terrorist, I still don't see how it's evidence that India did anything. The article about suspicious deaths even lays doubt on the claims: While his supporters claim that he was poisoned, reports suggest he had been suffering from blood cancer. The UK police later said they were not investigating the death because it was deemed “not suspicious”.
Either way, the point still stands that there is no evidence that has been presented. The constant claim of "we have 'credible' evidence that we cannot share" is a song-and-dance that I've seen too many times. Am I saying India didn't do it? No. Nor am I saying that they did it. The statements have had a negative impact for security both for Indian and Canadian citizens. At the very least, it would be in the public interest to release whatever evidence they claim they have.
If you've invited a lib into your apartment, it's entirely on you. Don't be surprised if they start colonizing your apartment and call it "Aid" or "Democracy" or something.