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.
For me it is not the problem of bitcoin but a problem of abusive users.... Everything will brings negative if you use it in negative ways so its up to the user if they will used it in legal or illegal purpose.... Yes... There are a lots of reported problem about the uses of bitcoin.... We didn't know that a lots of illegal transactions happening here.... We cant calculate everyone idea.... Maybe as a cryptocurrency user we should be the one who are responsible for our decision if you want to use BTC to make your successful or you want to use it to destroy yourself.... Its up to us....