Your last line seems totally contradictory to everything you wrote though. You have been actively involved in stopping/catching thieves and that is to be highly commended, especially as you put yourself in harms way which as you stated even the staff were reluctant to do.
However, given all that I'd think you'd be understanding then if a shop requested a check. Don't you think if everyone immediately takes offence and storms off that some shop staff might then think twice before doing a random check or checking a known shop lifter as they don't want the hassle. That way the criminals win.
It's one thing to see people stuffing stock into their clothes, or into a bag, with no intention to pay for the item(s). Another to make the accusation once they've left the shop floor.
I've set the door alarms off on entry, there's metal in one knee, which can create enough electric to set them off.* I'll watch it going out, so as not to "cover someone else" going out. I'd been in one shop to collect something that had to be ordered in, leaving I'd nothing but set the alarm off. Immediately a shop assistant was in front of me accusing me of "nicking stuff" as the alarm couldn't be wrong. Despite intervention by the manager, who'd been the person I'd seen at the counter, he persisted in his claim. Even when I stuck just the one leg through the barrier/gate, setting the alarm off.
This latest shoplifting epidemic is down to the stores wanting you in and out as quick as possible, which is why they're letting you use self scan, scan and go and unmanned checkouts. Despite many longer serving staff, in stores, saying what would happen. It has and the result is we're no longer trusted to use their systems, introduced by them to lower staff numbers.
The other is that retail theft has a lower limit of £300 in most police forces before they will get involved. The "typical" shoplifter knows this and aren't bothered about being challenged. They'll spit in your face, some even carry sharps, not afraid to stick you with them either.
I refuse point blank to use these easier/faster methods of shopping, mainly because they're taking away staff, but also because I don't trust them. The only time I've been made to use them, by an irate staff member
"you only have three items", the entire system went down. No-one could pay.
*There's very few shops left using those small plastic cased stick on security tags that use metal plates to generate a faint electric current these days.