This is the first time I've ever been solidly on the fence over matters pertaining to free Internet, free speech and post-Snowden discussion. I usually sit decisively on the no snooping side, but this is some serious gray area.
I have zero disagreement with the FBI locating, raiding and compromising the servers of someone like McGrath. His offenses were blatantly illegal as are the intentions of anyone visiting his content. Now, if the FBI were allowed to wield this type of wiretapping on ANY website simply because they can, then I would have a problem and concede the /potential/ for abuse. In this case it seems fully justified however and the line black. Just saying that makes me feel like I'm making concessions, but this is the kind of work I DO want to see happening online.
My hopes aren't high that checks are in place which would prevent abuse, so there is some concern. However, freedom of speech & privacy and freedom to exploit minors (or murder or do anything else deemed unacceptable by the worlds free societies) are most certainly not comparable. Online or in real life, I would want this sort of offense eradicated. I would challenge anyone who admits to wanting that much "freedom" in real life.
I think it's important to point out that ToR is not the vulnerability here either. The websites you visit are. This is no different than your unsecure Internet. Perhaps ToR can take steps to make this type of vulnerability impossible, but its not like the FBI can just flip a switch and do this with any website right now (or so I'm led to understand by this article).
I am truly bugged by this FBI matter but I am also ok with it. In this instance they got some really low lives of the street and they will be know to the police. What bugs me is did they have to go to court to all this, if not it sets every law that was created to protect against police abuse back 10 years. Also the police have lately been very loose with their interpretation of the Constitution.