In general, I think it is important to have accountability in policing so I agree with the idea of organizations like Copwatch or Copblock. The intentions of Copwatch are to report incidents of police brutality or other misconduct when it is observed. I think citizens should be doing this anyway, so having a forum for them to easily report is great. On the other hand, Copblock is a lot more anti-police.
There are pictures of people on the main website of Copblock with obvious hostilities towards police. This site may be dangerous and lead to violence against police. I think it is important to look at both organizations individually.