Everything comes with good and bad its how we use it that matters?so why should decentralization be any different.
You have a point there. You can't blame Bitcoin or the decentralization for issues like dark market and ransomware. These were not the intended uses of Bitcoin and we should rather blame the individuals who use Bitcoin for these purposes. In case Bitcoin is not available, then these people will just shift to another medium for their criminal activities.
I think only bad people who use bitcoin as one of the crimes like what happened some time ago, the attack spreads through viruses that are spread through the internet and that is an action that makes bitcoin have a bad image among the people.