George Floyd's murder was justified
The role of the police is to prevent crime and to protect society from dangerous individuals. The police were responding to a call from a concerned shopkeeper when they dealt with George Floyd. While the situation might have spiralled out of control, Derek Chauvin was doing his job. Unfortunately, accidental deaths stemming from police intervention are part and parcel of American society. This is a necessary sacrifice for social stability and functioning democracy.
Rejecting the premises
In the statement "George Floyd's murder was justified", the statement itself is a contradiction in ideas. Murder is a crime. In essence, it's a killing deemed to be of a criminal nature. Conversely, if the killing of another is justified, then it wouldn't be a crime, and hence wouldn't be murder. A better phrasing would be, "George Floyd's killing was justified". Although even that language is flawed in that it presumes that George Floyd died by homicide, which, at this point (7/2/20) is not certain. He could have just as well- and I would argue, probably did- die of natural cause and/or overdose of narcotics.