In theory this is true if everyone is being a well-intentioned actor but anonymity can be used to distort a broader agenda into an appealing message; see obscured-funded lobbying campaigns.
Also context is important for whatever one says, and a statement hanging on its own is rarely very convincing. It can be a red flag (whistleblowing) and it can be inspiring (famous quotations) but usually an argument is stronger as a result of the context from which it came (a culture, a person's stature, reputation, etc.).
That all said, I think we need to have anonymity, pseudonymity, and also verified identity. If we choose to share across those boundaries (sharing Facebook details with another service, as an example) then we have to deal with and accept the drawbacks. We can't expect to have isolated identities exactly the way we want them given that that kind of system would be a quagmire for developers to build...
Unfortunately an even larger subset of the population doesn't need anonymity to act nasty to others, while their victims often need it to prevent it escalating. Google's attempts to force real names on Youtube comments to reduce spam and bad behavior have been... less than impressive in effect. In a lot of discussions if you force real names you ensure that those with the most to lose (and often the most at stake) are also the most vulnerable.
Even presuming that counter to actual experience the generic trolls are deterred by a real names policy, there are others who become a much bigger problem when they've got access to real identities. Why do you think doxing is considered such a big thing? SWATing, offline stalking, physical assault, etc. are all risks as soon as a harasser has your info. Even worse when you're talking about something like domestic violence support groups there's a very real danger of the abuser escalating if they discover the victim has been talking to other people. That's 2.1 million people in the US alone who report physical assault by a partner in a single year who could really use access to resources without revealing themselves.
