Bitcoin is clearly not the main problem, but it helps criminals to laundering money easier.Bitcoin is in fact use for people and criminals to hide money from governments for many reasons. If they had to use US$ the laundering is more difficult. Using Bitcoin the laundering is much easier because it can be value transfer between individuals, across international borders, and so forth. Using dollars is easier to track and catch criminals.
I agree with you that bitcoin is not the main problem because even the paper money that bank or government controlled can use in money laundering. The problem is us (not all) , some are too greedy to get rich in instant in easy way and effortless then we become victim or suspect in money laundering .