I'm just going to lay out exactly how I feel about this situation from what information I've taken in.
These UC Davis students felt a need to exercise their constitutional right to peacefully assemble in the wake of the Occupy Wall Street Movement. Whether or not one agrees with the movement, it is difficult to blame the students for their support, keeping in mind the rising tuition rates, lack of jobs after graduation, etc. In order to effectively spread their message, whatever it was, they needed attention, and an excellent method of doing so is congregating in an area where people will actually see and hear you. They chose that pathway, which seems to be in the middle of a rather large, grassy area.
Annoying? Maybe, especially if you don't agree with their cause.
Inconvenient? Again, maybe, but walking (or most likely biking) around the students is well within anyone's capabilities.
Violent? Absolutely not. They are hurting no one. They are breaking nothing. They are vandalizing nothing.
Now, on the issue of their obstruction of a public pathway, I agree that this could be a real problem. If protesters decided to gather in the middle of a heavily used road or highway, that's clearly an issue. Cars can't just drive around them on the sidewalk, there's no way around them. However, going around these UC Davis protesters is a slight inconvenience, if anything. Hence, their spot of protest worked for two reasons: It was attention-grabbing, and it was no big issue for other disinterested students, staff, and passersby.
For the police to use pepper spray in this situation, is excessive. To utilize it from a few feet away like that is completely unnecessary and cruel. Faces are coated with a plethora of chemicals, and the cop doesn't just spray them, he goes back for two layers, painting the seated students. The use of pepper spray is not to be taken lightly, it's serious stuff. And this campus police officer was far from reluctant to use it on the students he's hired to protect. He very well could have used a light spray, but, like it shows in the video, he goes up and down the line, including a couple students that weren't even on the pathway. They were seated on the grass.
Right now, that police officer is on paid leave, which, I believe, is hardly justice.