I get what you're saying.
If the Black Block had resisted arrest and woken up handcuffed to a hospital bed, or even not woken up, I'd have said that they got their just deserts.
Paramilitary police going apeshit on silly students and naïve do-gooders. On a bad day, that proposition has it's attractions too...
Civilised head on: Not unless society is on the verge of outright collapse. The police exist to uphold the law, not to break it. Next year, it could be you and yours getting truncheoned into a coma.
Serious head on - if the grown-up members of whatever protest group l was stupid enough to hang out with at a demo or sit-in had decided to bugger off before the Eyetie or Polis Scoatlan riot mob rocked up, and l didn't follow them, whatever happened when they did come steaming in would be on me.
But there are vanishingly few things I would be ever seeing the need to go on demonstrations against, so the likelihood of me having a trachea/truncheon interface because of police reaction or over-reaction at a riot or demonstration is pretty small.