This is not an attack on bitcoin, this is an attack on Mt. Gox being non-compliant with KYC/AML/Registrations requirements. DHS has seized Mt. Gox assets. They are not going to seize wire transfers from Mt. Gox to customer accounts, nor are they going to seize the assets of compliant exchanges. This episode just reiterates that bitcoin exchanges need to follow the letter of the law or the hammer is going to come down. It's a shame, really, since Mt. Gox has the cash to spend a few dollars hiring decent lawyers to ensure compliance.
The compliance to some stupid, perverse law imposed by a gang of thieves and murderers that is completely broke, and about to fall apart?
This is, quite obviously, an attack on Bitcoin. Compliance, ultimately, means keeping your dollars, and watching them become worthless.