I think part of the issue is also that they had people in custody that are now in their care. That protest was one beer bottle, one punch, one shove, etc.. away from becoming violent. Once you surrounded the officers that is most definitely a threat of violence. Also the chancellor of UC Davis called the police to have them remove the people that had left their tents there after being told to remove them from the quad. They arrested the few people in/with the tents then attempted to leave with those people at which point they ended up being surrounded and blocked. Then they were given an ultimatum of let them go and we'll give you a moment of peace.
Civil disobedience has been used for a long time to get points across but that's just the thing it's disobedience just because you do something nicely doesn't mean you're gonna get away with it. The protesters got their point across and now maybe the rules will change and people will be allowed to stay there in their tents and "protest". However at the time that was not the case.
I don't fault the police and I also think the "protesters" that got pepper sprayed are great for standing up for what they "believe" in. You can't fault either side. This is the kind of thing that this country is great for and also what gets things changed. If the protesters just gave up then they would be pansy bitches. If the police let them do whatever they want then they would be pansy bitches not doing their job. When things like this happen it brings the attention of wrongs to the forefront and allows them to be discussed and changed.
Rosa Parks is a great example.