Following Alister McGrath, I’ve come to think that the reason why we should love the church is none other than the fact that it is an actual social reality of Christianity.
Christianity is a religion centralizes on the person of Christ. Hence this centralization makes it distinct from other religion (just ignore the weird “way of life” description of Christianity). And the church as an artifact that preserves the tradition of Christ, which has since been written down as scripture. It is said that Christ has bestowed his glory to the church (John 17.22).
On the other hand, the church is no less than the fellowship among believers. It is also a worshiping community. And the danger is to rest the definition of the church as just these and nothing more.
The idea that Christianity is the working definition embodied by the community of believers is robust enough to engage in our ideological-infested world. The church serves as a social structure in the public to speak to it. No doubt the reasons to love the church are many but the fact that it is the social identity of Christians, Christianity, and Christ should not be forgotten.