Er, no. Witch hunts aren't from anonymity, or there wouldn't have been any back when everyone lived in little towns where they could be instantly & easily identified by just about anyone else there.
Witch hunts often come about for the opposite reason, in fact: it places immense psychological pressure upon someone when they see others around them (particularly people they respect) targeting individuals or groups, and because the "us vs. them" attitude means that even appearing to sympathize or disagree means potentially being targeted as "one of them," the vast majority of people will go along with it. Even if there's no threat of physical harm, being socially ostracized or looked down upon by others that know them (particularly ones respected by the community) is stressful enough to impel most to cooperate, particularly if the group includes individuals that the person wishes to be respected by and/or that are higher in the social hierarchy.
In-person, people gossip and speculate about others they know with friends, co-workers, or others they're on a first-name basis with, often despite knowing that the "information"-sharing could or will cause grief for the individual down the road; if the friend/co-worker starts speaking negatively about someone else, again, the majority of people will refrain from speaking out against it for fear of either hurting their standing with the person or becoming the next target. Likewise, it's similarly highly common for kids to gossip, knowingly lie about or even bully classmates as a method of bolstering their place in the social hierarchy, and very few kids will speak out against someone their age that's engaging in that kind of behavior.
The idea that anonymity leads to anti-social behavior online was nothing more than an untested theory that the media picked up on and ran with, not a well-established psychological reality. The few studies that have been done (including examinations of forum results) indicated that requiring real names only eliminates a tiny percentage of the vicious posts or trolls. That's because the vast majority of people that troll individuals or groups feel there's absolutely nothing wrong with their behavior, very often even feeling proud of it; they'll say the same things whether they're logged in under their real name, a pseudonym, or anonymously, which is why *Facebook* has a huge problem with bullying & trolling by people using their real names. (Think about all of the times you've seen people express smug pride for being "politically incorrect" by needlessly using slurs or saying things when somebody politely says it's hurtful to them & others -- the same callousness appears on Facebook and other places where people post under their real names.)