I can see how one might think so. But not all police officers are required to carry weapons. In some countries, policemen do not carry weapons at all.
For Jehovah's Witnesses, the concern, of course, is that an officer might need to pull a weapon and use it. That opens up the possibility of incurring bloodguilt.
A good friend of mine (she died some years ago) who was in the same congregation as I used to be a police officer. She wanted to become a Witness and spoke with the elders to solicit scriptural counsel on this. In truth, I do not recall the outcome. I seem to recall that they told her she could remain a police officer. Again, I do not remember the particulars. It may be that she was a detective and did not carry a weapon.
I am aware of police officers who are Witnesses but they are not armed and do not "serve and protect" on the streets. There are countless positions open with police departments that do not require such.
What do I think of police? I respect them and admire them and I am happy they are there to try and protect me. They have such a difficult job - particularly in these violent days. Back in 2014, at our International Convention, there were a couple of uniformed officers on site. (They always send cops initially as a security measure but they end up leaving because the vast majority of us are brothers and sisters and we do not require crowd control or anything like that.) We had a ball with them. They were so nice and friendly. They stayed awhile to listen to some of the Bible discourses and took pictures with many of us. It was great.
I could never be married to an armed officer. I would be terrified that one night, my honey just would not come home.
Thank you for your question.
Hannah J Paul