Seems to me, more often than not, education works well with the uninformed.  When that fails, I go up the chain to someone the detractor cannot say “no” to:

• You are likely in agreement with your manager and so allow them to address the issue.
• Often they are more familiar with the best approach with this staff person or can simply say “we are doing it this way, end of story.”.
• If they attend management meetings, use that time to elaborate on their concern, allowing others to chime in with reasons to back up your desired approach
• Find out their “real” objection to your plan
  • Do they have something already planned that is similar?
  • Are you adding to their department workload?
  • Will they be impacted in a way they haven’t shared?

Objections to your project planning can be unreasonable or without logic.  Using upper management or an SME (think security analyst) can assist with keeping all the work put into your planning from being undone.