I don't see why someone would just become addicted to something like VR if there wasn't something puching him into it. For your theory to work you would have to say that Barclay is a neurotic because of the Holodeck and leaving it would cure him. Judging from his other episodes it doesn't..
Fortunately we have some exact parallels in modern life that are becoming more and more prevalent. For example, people become addicted to fantasy online games all the time. Some of these individuals might have pre-existing conditions, or a tendency to flee from reality, while others simply spend more and more time and energy on the fantasy world to the point where it disrupts their lives more or less severely.
There is no need to postulate cruelty or abuse on the part of others to explain this behavior.
Riker, Geordi, and Wesley all had no idea Barclay was a VR addict when they started bullying him with nick names and such.
No, they do not understand the nature of his addiction, they think he is just slacking off and disinterested. Part of what happens over the course of the episode is the crew, or at least certain members of it, especially Geordi and Troi, come to a better understanding of what Barclay is coping with.
They are insensitive and callous along the way, but that is part of what makes the episode compelling. This reaction is unfortunately very plausible, even in response to more widely known conditions such as depression.
And if Barclay's addiction to VR was solely his own problem then why was his fantasy life about torturing his crewmates? Obviously he's in the holodeck to get even for his treatment. That's about all I can possibly say on the matter.
It isn't solely his problem. It is everyone's problem. I think the episode deals with this pretty directly. Barclay's behavior is of a cyclical nature and certainly involves the crew.
I don't think it is accurate to say, though, that he is in the holodeck to get even. It is a coping mechanism, albeit a self-destructive one.