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.
Crime is not about Bitcoin. Bitcoin do exist because people want it to exist for it helps lot of people to earn extra income that may help them by providing the needs of their family. Crime may use Bitcoin to do so but its up to people if they are going to believe on the scammers or not. Not all part of intermet is bad or can commit crime it can also help people to know what they want to know. Its just that people uses internet because it is the easiest way to do crime.
Unfortunately, you are right. There are bad people who are using Bitcoin because it will be easy for them to have transactions. But these people are the ones responsible for this act. Bitcoin is Bitcoin and those criminals are criminals. Be more knowledgeable because in this industry you really need sources to survive.