If you actually bothered reading my detailed critique of the containment tactic you would know that I have criticised how it has been used in a number of ways since before G20, with many of my concerns being reflected in the HMIC report "Adapting to Protest" too.Frankly, I'm not that bothered with your defence of police tactics, that are clearly raising concerns amongst a sizeable section of the populace. Specifically, people who would normally be supportive of the police.
The vast majority of the public would have no particular problem with the tactic of containment and would see, if the media were responsible enough to explain how and when it's use may be appropriate, to realise that it has a time and place when it's use is entirely justifable.