Anything can be used for illegal activities.
I think that the main reason why btc has been rejected by society is that there's still much to learn about it and it's easier for them to speak ill of it than to try and deal with it.
I agree with you. Fiat has been you for many illegal activities for over centuries and no one actually wants to reject it. As long as bitcoin keep developing, no one can ban it or even ignore it.
yes it is not necessary to think about that either bitcoin is used for illegal activities or not, because all other fiat currency may be use for illegal activities and still no one really reject to use it, so we have to give concentration to the improvement of bitcoin.