I wasn't aware that Scientology used physical threats against their opponents; I guess I do need to read up on the subject. Can you recommend any good places to start?
That being said, the particular case under discussion doesn't involve threats of violence. It hasn't been reported that Cruise is setting fire to Viacom or roughing people up outside of Paramount headquarters. Of course, given some of his antics, I won't say those things couldn't happen in the future. Still, all he's done so far is to threaten to not do business, and that isn't censorship.
http://www.clambake.org/ is the most comprehensive site.
Actual violence is rare, at least against non-members. Here's the story of a member who tried to leave and didn't get out alive http://www.lisamcpherson.org/ And threats of violence have been used against concerned relatives of members http://lermanet.com/idacamburn/ . Blackmail/framing is the usual MO, and is used against members who have been coerced into performing illegal acts while Scientology documents them, and against non-members who have been lured into Scientology front groups, which gather a lot of personal and financial information on them. One of their ruses is to set up practice management consulting firms targeting unsuspecting doctors and dentists. And they're fond of bankrupting individuals and businesses who criticize them, with legal attacks.
There is some evidence that the rise of the Internet is putting a damper on a lot of Scientology activities, as it's much easier to get and spread info about them. Tom Cruise has done a heck of a job too, what with the whole Katie Holmes affair, and his going off on Brooke Shields on national TV (in case you missed it, he went ballistic on her on a talk show, because she had used medication to deal with post-partum depression).
One particular thing to be on the lookout for: ANY individual or group which claims that there is "no such thing" as attention deficit disorder and that NObody is helped by medication for it, is either affiliated with Scientology or under the influence of people who are. One of their big money-makers in recent years has been setting up front groups which claim to provide drug-free "therapy" for ADD. Very expensive therapy, of course. This has been hugely successful, since they're capitalizing on the epidemic of incompetent school officials and parents whose practices have resulted in hordes of out of control kids, who the same incompetents then try to control with Ritalin and similar drugs. There's a huge pool of parents who correctly believe that non-drug methods should be tried before resorting to drugs, and that "diagnoses" of ADD are often unfounded. But frankly, any kid -- with or without real ADD -- is better off on Ritalin, than having their whole family tangled up with a Scientology front group.
To split semantic hairs, violence and threats thereof, from a non-government entity, isn't technically "censorship" either, but it's at least as bad.