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 wouldn't pay any attention to this nonsense. Whenever a new technology comes about it's inevitable that it will be used by criminals. They are always looking for an edge. Look at when the Internet came about! It was all about sex, drugs and fraud they said. Now look what it has become. I can see the save evolution for bitcoin/cryptocurrency