Yes it is used for some criminal activities but we should not care about it at all because this is life, the fact is that every currency has this down and dark side.
I do not care and I think its also logical and not so bad too.
yes that is a fact that it can be use for some illegal activities just like other fiat currency like USD and Euro and almost every fiat currency but there is nothing wrong to bitcoin and bitcoin is not responsible for these illegal activities as it is just common in every society and in every currency.