It may seem like petty semantics, but pastors can bring scorn on themselves (in some denominations) if they deviate from the traditional order which is: believe --> belong.
So here are the twin questions that fuel the squabble:
Must believing in particular Christian doctrines precede belonging?
Can belonging precede believing in particular Christian doctrines?
My experience has shown that both scenarios are possible.
On the one hand, there are people who are detached from a Christian church, but they encounter and believe the Gospel of Jesus. They subsequently seek out a Christian community where they can experience "belonging" with others who also worship the God and Father of Jesus Christ.
On the other hand, there are people (most commonly called "seekers") who show up amid the Christian congregation. They hold no Christian convictions themselves, but they continue to be present at the weekly gatherings of the church. They are encouraged to seek truth and are embraced as friends, and some will eventually find themselves believing the Gospel of Jesus.
I don't know anyone who would argue against either of those two scenarios, so the crux of the questions above is what we mean when we say "belong."
When leaders of traditional churches talk about "belonging," they're - usually - referring to the family of God, or the body of Christ (both are metaphors used for the church in the New Testament). In that case, they're right to say that some people don't yet belong...and if they want to belong, then they must believe.
That's why traditional church leaders insist that believing must precede belonging.
But when leaders of emerging churches talk about "belonging," they're - usually - referring to the public worship gathering that is open to anyone and everyone - Christians and non-Christians, seeking and apathetic, friendly or hostile.
But there is an inner circle of "belonging" that is entered only after "believing." This is the circle of familial responsibility and accountability that should not be minimized, lest the church implode on itself for lack of definitional boundaries.
So the questions we began with can be answered: Yes and Yes.
Spatial Relationships, Belonging, & the Church
Elements of a STICKY Sermon: Kerygma