Apparently, joking and making humorous remarks about something that you know you can't stop means that you're automatically in league with them. Because, you know, that's totally how society works.
Now, I'm not saying they weren't in league with the pirates... but that there isn't enough proof other than a lot of "allegedly" and something about the abuse tool being limited (Which I would think would be standard practice, in order to prevent the abuse tool from being abused, naturally) and a whole shit ton of he said she said bull shit.
There is not nearly enough evidence for this bullshit. It's fishy as hell.
Someone else put it best - they should have, at most, seized the US servers and then prevented US access to MegaUpload. At least it would've been easier to settle an intracountry dispute than an intercountry dispute.