It is a painful irony of our time: when a new face enters a Beis Shmad i.e. a missionary "Messianic" congregation, they are immediately enveloped in warmth, often greeted by a designated "welcome committee" whose sole job is to make them feel at home. Why? Because they want to shmad every person they can and a warm welcome will help him feel at home.
Yet, so often, when a new face appears in our own shuls, they are met with silence, or worse—ignored. We have all seen it and experienced it.
We must remember that a shul is called a Beis Knesses, not merely a Beis Tefilla. While it is a house of prayer, its essence is the Knesses—the gathering. It is the place where the Jewish people come together to form a community. If we do not connect with the Jew standing right next to us, have we truly gathered?
When we daven, our nusach is phrased in the plural. We don’t just daven for ourselves; we daven for the welfare of all Klal Yisroel. That stranger in the back row is the very person we are mentioning in our Shemoneh Esrei. It is a spiritual contradiction to plead for a fellow Jew’s well-being in our prayers and then ignore his presence. It would be a beautiful קידוש השם if our "gathering" lived up to its name.