The first rule filters out vandalism, soap-boxers, spammers and other random ne'er-do-wells. The second filters out those who refuse to discuss, debate, make or accept norms or rules, etc.
Everyone else should probably have a place at the table, so to speak. They'll at least be amenable to discussion when conflict occurs, and will try (hopefully) to resolve the conflict in a way that benefits the community by reaching its goal.
See also: IntegrationAndIdentity
Without a RightToFork, you raise the stakes of the conflict. So, conflicts are going to be more extended, more vituperative, more difficult. RightToFork is a pressure release. If not forking is more important than reducing conflict, sure, don't allow forks.
A better solution would be for the community to accept a wider range of opinions, and EnlargeSpace so that conflicting ideas and interpretations have room to grow within the same tent. For instance, there is rarely any technical justification for forking a wiki page because you disagree with its tone or conclusions as you have the opportunity to add your opinion directly to the wiki.
The critical question is whether the desire for a fork is due to social conflict rather than a conflict of a more philosophical or technical nature. -- SunirShah