My comfort level with police depends on where I meet up with them. If they are shotrim, Israeli police, I feel protected, and embrace their presence. I know they are looking out for me, and my loved ones. Even though some may seem rude, or impatient, they still have my best interests at heart – even though they may give confusing and conflicting directions (seemingly on purpose).
However, police outside of Israel, as polite and friendly as they usually are, always trigger wariness and an increased heart rate. My parents were Holocaust survivors from Poland, who were rounded up, as were their families, by physically brutal and emotionally sadistic Polish and German police and sent to various slave labor and concentration camps. They witnessed the indescribable, and were themselves the recipients of inhumane and pitiless actions by the police.
Traumatized, they never lost their terror of policemen and their power. They would be terrified when one would approach the car they were in, even if they were passengers. We children knew to stop bickering and be quiet. We internalized that fear.
Having said that, the vast majority of police officers are altruistic and brave individuals, who have taken on the very difficult job of protecting people and keeping them safe. We should be machmir in expressing hakarat hatov to them when the opportunity presents itself.