ive been drinking in pubs nearly 50 years. I can tell you from personal experience the levels of violence have escalated ten fold since 24 hour drinking - ask and police officer of A&E doctor, its clearly the case. People got drunk on the old laws, but its the scale thats the problem, theres now 953,000 cases of drink related violence every year, which is ten times the year before 24 hour drinking was introduced. To try and argue there isnt a problem is being blind to the facts and the truth.
I don't know where the true facts lie...
For example:
http://www.timesonline.co.uk/tol/news/politics/article7014059.ece
There are too many ways to interpret the figures, maybe the police are less likely to arrest people for being drunk due to paperwork, maybe people charged with violent crimes are being dealt with less harshly by the courts, and are re-offending, maybe the price of alcohol is a factor, unemployment? recession? rising popularity of UFC?
People who get into fights when they are drunk will do so at whatever time they get drunk. So pubs closing earlier will just move the problem to a different time.