Anti-police sentiment

Anti-police sentiment refers to a social group or individual's attitude and stance against the policing system. 
By country.
United Kingdom.
Contrary to its European neighbours England did not have a tradition of professional police forces. Crime prevention was carried out by a combination of the town watch and the parish constabulary appointed by the justices of the peace in each county. In Great Britain during the late 1790s, anti-police views were based on the possible encroachment of absolutism through professionalised law enforcement, the obstruction of the magistrates' power and skepticism towards trusting an unfamiliar organisation.
United States.
In the 1950s, William Westley suggested that anti-police sentiment may come from the social stigma of working in dangerous conditions, having to work with stigmatized others, and at times unethical practices.
In the 1970s, police departments began to become concerned about litigation over police misconduct.
Distrust of police in the U.S. is sometimes mentioned in connection to police brutality and racial profiling.
In 1991, African American man, Rodney King, was savagely beaten by four Los Angeles Police officers. The following year, the 1992 Los Angeles riots broke out in response to the acquittal of the police officers involved in the beating. This event brought large amounts of media attention to police brutality towards minorities such as African Americans.
The 2014 shooting of unarmed Michael Brown in Ferguson Missouri and the ensuing outrage is considered a turning point in the U.S. dialogue of the "war on cops" with the Black Lives Matter movement challenging the legitimacy of the police.
Minority groups in disadvantaged neighborhoods tend to distrust police more and feel that the "law is not on their side".
The role of police in the restriction of youth freedom has also perpetuated anti-police sentiments among young people.
President Trump has on several occasions condemned the anti-police atmosphere.
Media.
Smartphones, allowing people to capture real-time recordings of confrontations with police and spread them across the internet, have been mentioned in helping extend anti-police sentiment. A narrative from mass media and spread through social media may reinforce a "us vs. them" mentality that is detrimental to society's relationship with police.
Anti-police sentiment also manifests in hip-hop and other forms of music such as rock and nu metal.
U.S. police response.
Police have expressed feeling threatened by violent protesters and attackers, and a dissatisfaction with a larger gap between police and the community.
Some have blamed media for fueling anti-police sentiment. Chuck Cantury Howard Safir identified "a war on police" in his letter to President Barack Obama. Former FBI director James Comey addressed in 2015 by positing that "a chill wind [is] blowing through American law enforcement over the last year… and that wind is surely changing behavior". Academics have theorized that "de-policing" may be seen in America as a response to police dissatisfaction in some areas.