If folks are trying to resist/stop arrests..then they are asking for trouble.
Are you really saying that if someone disobeys a police officer then anything that officer does to them is OK?
Have you seen the video? The use of spray was not on anyone who was in any way a threat.
There is an issue of proportionality you're failing to acknowledge, even before we come to the justice of a given protest's cause and methods set against the police's role of defend the target.
As a taxpayer, I don't want to be paying the bills for the damage / havoc some protesting marches will create
In this instance we're talking about an arrest for putting leaflets through a door. A door to Boots which was so not under attack that staff members treated those attacked with CS spray.
Even if we ignore the justice element and just go with your tory pounds and pence vision, what do you think the comparative costs are of arresting and detaining someone versus not doing so and permitting the 'havoc' that ensues when they put a leaflet through a door?