Yes, it is very much possible to launder money with bitcoin and I am sure there are already many cases of this happening. This is also how most of the sites like bitmixer survive and are able to pay those big amounts out on signature campaigns. Since it allows people to be almost anonymous, therefore it is and will always be the best way for people to evade taxes and launder money. It is also the reason some governments are against it.
We know that bitcoin transaction is kept on blockchain which allowed people to traced it, the transactions are never truly anonymous.
Many illegal activities going through bitcoin but the evidence still there, including money laundering.
However, my concern about sites offering to mixer bitcoin, so it can't be traced right? But, I don't think those mixer sites will easily accept money laundering.
That's why some countries issued regulations about bitcoin and exchanges to prevent any kind of those transaction.