“I however do not understand the need to own an assault rifle for private use”
You don’t need to. You are a public employee hired to keep the peace, show up after a crime has been committed and make out a report. Its not your job to philosophize about why the constitution says the general population has the right to bear arms. Its not your job to ascertain what kind of weapon is appropriate for citizens to own and its not your job to wonder why they want to open carry. Just be glad you have a job and that these good folks would be the ones backing you up if you got into a situation you could not handle.
I respectfully disagree. This officer took an oath to protect and defend the Constitution of the United States against all enemies, foreign and domestic. It appears to me that he should be using his forum to defend the Constitution, rather than denigrate it.