How would you avoid the conflict of your trucking office staff in the future?
First of all, instead of imposing hierarchy and show your power, approach the problem as only great leaders would do.
Respect your employees.
More importantly, respect their differentiation and contrast of opinions.
On top of that, you need to get to know their personalities and who they actually are apart from their professional profiles.
First, you need to be able to understand their behavior.
Second, you need to lead them through the process of upgrading themselves.
Consequently, make them work on their behaviors and respect the characters and opinions of the rest of the trucking office staff.
To put it in another way, you need to teach them that same as they are successful in their work, they need to be successful in working as a team.