This may have been asked, but when was the last time a peaceful protest actually got a decent reult?
Arguably, this one got some sort of result -
http://www.bbc.co.uk/news/uk-11508226
Initial threats of a 25% cut were scaled back to a freeze on funding.
I think it's very difficult to say how much effect peaceful protests can have. You can never know what would have happened without the protest taking place.
As far as the current protests are concerned - I don't have an objection to a bit of "violence" as long as it's against property rather than people.
I'm not sure the whole argument about garnering public support is as clear cut as many here like to think it is. Yes of course the violence etc gets the protest more coverage. I'm sure it does turn a significant number of people away from supporting the demos, though, particularly with the way it's reported in the mainstream news etc. Whether that matters is another question of course.
What is perhaps significant about these fees protests is that a lot of people attending them (as far as I can make out) aren't your usual activist sorts. Lots of well-to-do kids/students with well-to-do parents who will hear their accounts of what actually happened; the whole kettling thing etc. Maybe a certain segment of the population will question things a bit more than they usually would.
I do think it's important for the protests, violent or otherwise, to be backed up with a strong effort to present the arguments against the fees increases and the cuts generally, in an objective way, thoroughly backed up with the relevant numbers and so on. That's the way to counter the tendency for many to see the protests and think, it's a bunch of students making a kneejerk reaction to proposals that aren't actually that bad when you look calmly at the details (as per the line being pushed by Cable/Nick Clegg).
I know that many don't think that the views of the middle classes are really relevant in all this - but, well, I do and I think there's a good opportunity at this moment to get more of them on side which I hope won't be wasted.