There is a huge gap between not giving a presumption of trustworthiness, and using deadly force. The police and the legal system are not trustworthy, IMO, but use of deadly force is only justified when one reasonably believes he is facing serious injury or death.
The number of times cops use deadly force without justification (and this is a case of that, based on what I've read) is vanishingly small compared with the number of police/serf interactions.
A very large gap, that is true. However, the trend could very well bring the situation to extremes.