I have seen some news regarding hackers, terrorists, and other criminals using bitcoin for illegal trades.
How the police can find about these transactions?
Even if is hard to track illegal transactions, I don't think that Bitcoin can be a danger to society, since the problem is the society and its people.
Since the beginning of the internet this is happening ( the bad people committing crimes) and no one is willing to shutdown internet because of that, so in that matters Bitcoin should be equivalent. I think those illegal transaction are one of the reasons some governments and the media are trying to depreciate bitcoin, but the problem is not Crypto/blockchain or Bitcoin, is just the society.
I think any forms of money digital can be used by criminals in their bad activities the only different in bitcoin it is very hard to find the criminal and mostly government authorities don't have enough knowledge hoiw they can trace transaction considering that funds is transfer to different wallet addresses which is hard to identify the owner.