After Yosef revealed himself to his brothers, he sent wagons to Cana'an to bring his father and extended family to Mitzrayim. The Torah enumerates all of Yaakov's descendants and ends with a tally of those mentioned: "All the person[s] of Yaakov's household who came to Mitzrayim numbered seventy."
Rashi, citing the Medrash, comments that while the Torah only enumerates six of Eisav's descendants, the Torah refers to them in the plural: "the people of his house" because the few people of his house all served different gods. In contrast, Yaakov had seventy descendants and, nevertheless, the Torah refers to them in the singular: "All the person coming with Yaakov."Since they all served a single G-d, they are referred to in the singular.
Rav Wolbe (Shiurei Chumash, Vayigash 46:26) explains that the description of Bnei Yisrael as a singular unit was not meant to imply that they all had the exact same outlook on the world. A large group of people who all profess the exact same mindset in all areas of life is sometimes found among people devoid of spirituality. Those with a connection to spirituality will develop their individual talents and intellect into a unique approach to life which will determine the way they think and respond to any given situation.
Rather, Bnei Yisrael's quality of oneness was an expression of their living in harmony with one another (after making amends with Yosef). They loved each other and cared deeply about one another. Indeed, such solidarity is only possible if all those involved are serving a single G-d. When one finds a group of religious people who do not love and care about each other and are oblivious to the plight of those around them, it is a sign that they are not all serving a "single G-d." Such people must be serving the "gods" of desire, haughtiness and honor, for if they were truly serving Hashem then their service would breed love and friendship and not the opposite.
What is the secret ingredient that threads its way through all those who serve Hashem and fuses them into a single unit? It is precisely their common desire to serve Hashem - the single G-d - which unites them. One might be a fiery Chassid and his neighbor a mussar oriented Litvak, but as long as they are focused on the same goal, then love and friendship will reign. However, when personal desires sneak into their spiritual pursuits it will automatically promote animosity since every person has their own set of desires and preferences.
A difference in dress should not be the impetus for a lack of harmony. Distinctions such as wearing a velvet or knitted kippah, a white or blue shirt, a long or short jacket or a baseball cap or striemel, are not grounds for feelings of animosity. Nor should one's nusach ha'tefillah be a reason for enmity. If such differences irk a person, he must check his GPS to determine what life goal he is pursuing. For as Rav Meir Shapiro (the famed founder of Daf Yomi) put it, "Whether davening Nusach Ashkenaz, Sefard or Eidut HaMizrach, everyone joins together by Yehi chavod Hashem L'olam, because regardless of how one gets there the ultimate goal of every Jew is to bring glory to Hashem!"