The dark web is the World Wide Web content that exists on darknets, overlay networks which use the Internet but require specific software, configurations or authorization to access. The dark web forms a small part of the deep web, the part of the Web not indexed by search engines, although sometimes the term "deep web" is mistakenly used to refer specifically to the dark web.
Every affair in the dark web will use Bitcoin as a method of payment. In the dark web there are various illegal businesses such as the sale of illegal firearms, drug trafficking, assassins and hackers.
What are your thoughts on this Bitcoin abuse?
Yup! I agree with you

. The divers in the deepweb use bitcoins in their transactions instead of using conventional money. I think they use bitcoins because it's very practical (it's existing in your computer so it's easy to buy/pay) and it's safe to use in terms that you don't need to have meet ups therefore you are still secured and anonymous.
In addition, I've read an article that it can also used as payment for torturing adult people and even an innocent child.