The majority of attack against the Church of Scientology is run by a small group of apostates and professional intolerants. These people seldom do more than allege the Church has committed crimes and get those allegations disseminated across the internet. And since it appears to be more en vouge to bash something than defend it (especially when you know nothing about it) their campaigns appear to be successful. The actual fact is, their campaigns are not successful, based on the recent rapid expansion of Scientology.
I suppose these people feel they are doing the public some sort of service by attacking Scientology and other religions and religion in general, but all they do is propagate hate, intolerance and ultimately reveal their own criminal activities.
The old Cult Awareness Network (CAN) was known for this behavior, with Rick Ross being prominently involved. Here is a document from Cesnur on the topic.
Some of the more visible anti-religion and anti-Scientology names are:
Tory Christman ("Magoo")
There is a site run by a Scientologist called Religious Freedom Watch (www.religiousfreedomwatch.org) which documents information on the above names and others. There are a great deal of court documents and transcripts on that site so I won't repeat it here.
Study about the Cult Awareness Network (CAN)
Local mirror of CAN study