Your own post undermines your point.
"...easily on MegaUpload because that's basically what everyone was using it for"
You can never blame the creators of a tool for what their users do. Not to rehash an old argument, but you don't blame suitcase manufacturers for making suitcases that criminals use for convenient cash lockboxes. You can't blame a knife maker because a housewife stabbed her husband.
Unless you can empirically prove that MegaUpload courted people to break copyright I don't see what case you have. All of your "claims" seem to be anecdotal bluster, couched in a defensive posture to automatically discredit anyone who disagrees.
I find it so hard to comprehend that people refuse to believe that MegaUpload was never used for legitimate reasons. It's widely known that MegaUpload was well used in the corporate world[1], however it's unfortunate that no specific companies (to my knowledge) have come forward publicly. As a personal aside, I used it many times to send files that were too large for email to classmates and friends.
Beyond all of that, you are overlooking the problem. Attacking filesharing websites is simply slapping a band-aid over a symptom. The websites will continue to pop up, there is a demand and someone is going to supply it. Plus, it's incredibly easy to set up your own file-sharing website... I expect it won't be too soon before we start seeing people rolling their own just like blogs today (though admittedly not nearly as widespread).
We need to be addressing the real issue. Admittedly, I don't have a solution to "piracy" on a grand scale, however I can certainly say actions like targeting MegaUpload and then vilifying a business that has yet to even land a single customer over it's first press release definitely do not help the issue.
[1] http://arstechnica.com/business/2012/01/before-shutdown-mega...
Edit: phrasing