HSBC and Wachovia were recently involved in the laundering of hundreds of billions of dollars for Mexico's biggest drug cartel (and pretty much every executive involved came out unscathed once it was revealed).
When I bought drugs in high school, it was usually in cash. Sure, I concede multi-million dollar operations may have bank help, but I don't think you're thinking about the full picture.
One big difference is that cash is too popular to ban entirely. If a major attack were somehow linked to Bitcoin, the US government could make the whole thing illegal. We all know that wouldn't do much to actually stop terrorist attacks, but it would be a major problem for a wealth manager trying to operate within the law, and being ineffective certainly hasn't stopped the US government from passing dumb anti-terror laws in the past.