What about a chased round the corner and grap the first person you see there scenario?
Or catching someone red-handed of looking in the back of a van that someone else has just stolen tools out of?
If you see someone you don't recognise going into the back of someone else's van and decide it's time for a little summary justice only to proceed to smash the hands of their new apprentice/mate who's helping out for a day, is that OK?
I get the points you're making, Dave, but I've also seen the other side of similar issues. People losing hard earned possessions and it might take the police weeks to attend - if ever. "Take this crime reference number to your insurer" isn't the answer to this type of crime as it effectively endorses theft, by reason of losses should have been insured.
We aren't talking about the theft of a ham sandwich by someone unfortunate enough to find themselves homeless and without income. Tool thieves are generally well equiped with and able to make a quick escape with large and heavy items. Tool theft in the UK is a chosen way of life for gangs up and down the country - the same amount of effort in legitimate enterprise would generate significant income, but these people aren't interested in playing that game.
The statistics are out there as are court records, which represent only a tiny percentage of overall thefts. There have been a number of notable sentences handed down, but more often we see relatively light sentences handed out to people with lengthy records of similar theft.
Do I think beating the tripe out of a few thieves is going to make a difference? It certainly won't, but I wouldn't be too hasty to judge someone who took the law into their own hands in such circumstances - walk a mile in their shoes and all that. We've had a decent run of late in construction, but that's coming to an end and tool thefts are going to be the cause of many small businesses sinking as work becomes more scarce, operating costs increase and margins shrink.
One last point is that tool thieves don't stand around looking into vans and nor do they casually carry one or two items. When vans are emptied, it is usually with significant haste, zero care for damage caused and goods are slung uncaringly into a waiting vehicle. Method of entry ranges from expert with minimal signs of ingress to disc cutter used to open the side of a vehicle, but all have one thing in common and that's fast removal of tools and hasty escape - if someone making such an escape happened to run face first into a shovel, I might find myself struggling to feel much in the way of sympathy.