"Unfortunately, coins like bitcoin have no privacy embedded in their protocol. All the transactions and amounts traded between all parties are publicly visible. This prevents bitcoin from being fungible, and leads to fundamental problems with the viability of bitcoin as a global monetary base...

Monero solves these privacy issues by automatically applying privacy techniques to every single transaction made.

You can have confidence that it is not possible to own ‘tainted’ Monero. This is a concept in economics known as ‘fungibility’ and is historically considered an important characteristic for any currency to have."

https://agoradesk.com/how-to-buy-bitcoin-anonymously-without-id