"ויסעו מרפידים ויבואו מדבר סיני ויחנו במדבר ויחן שם ישראל נגד ההר"
The torah, as the "daughter" of Hashem contains secrets (understanding the deeper messages of everyday life through Torah) we can't uncover on our own. We need achdus in order to unlock the secrets of Torah. Only when unified do we have the spiritual energy to unlock the Torah without which we can't live. Thus we can't live without other fellow Jews.
The midrash, says they were כאיש אחד בלב אחד - it doesn't say that they agreed (בדעה אחד), just that there was unity - achdut doesn't necessitate uniformity.
Provided courtesy of rabbisilber.com