Profiling is bad, it creates more unrest than it solved, but I don't suppose when people having half-jokes sometime about black people drivers getting "pulled over" by police for
random inspection are more frequent than white drivers, in well established western society - they are making things up.
Not "defending" the profiling habit of security enforcements all over the world - but it dose helps in a sense to narrow down (outsider) terrorism threats. Terrorism threat, or a certain limited amount of civil right breaches, people made their own self-conscious choice - especially those whom their society already suffered successful terrorist attacks.
To your personal experience, I really believe they (the security services)
got you figured out before you present your ticket, and to their own past experience dealing with foreign passengers who "knows their own rights" which pretty much would takes time to arguing that certain personal properties are not proper to consider as contraband - would causing annoying trouble just to get their ass finally boarding, on top of most certainly language / communication problems - The equivalent smartass security officer(s) would simply rather take his chance and let you boarding the train with your nunchuks, while trust you would behave.
- That dosn't equal to "they let you take certain things to aboard".
It's still about "dealing with people" - allow me to say the cold truth - dealing with somewhat IGNORANT (annoying) Chinese citizens from all walks of life (well, most of time, poor lives), who smartass enough to know how to make things happen - is a far more tiring yet important (and sensitive) job to those who makes China's all kinds of transportation security a real (vs, a mess). Like I mentioned, a poor people hiding obvious contraband in his pocket (fire-crackers is cheaper in this place than that place, bring some fire-crackers as gifts to children at home), dose not intent to blow the shit up yet possess huge danger to China's day to day transportation security - and the security officers can not outright (read carefully
confisticate, disposs, the contraband goods, nor can they detain or arrest every person who is doing the same they met - China's social content / unrest, is not (only) about LAW, but more about JUSTIFICATION - you confisticate some poor man's hard earn money bought gifts to his poor child at home? outright? - what kind of heartless devil you are? How the hell you justify that? (at least to the mass folks)
Chinese security personnels (and pretty much every kind of public service), what they doing the most in the day to day job, is CLARIFICATION. If you can not "reason" the people to leave the controbands behind, if you can not gain the support from the crowded masses for your justification to take "legal actions" agains certain individual people (who is masked by "poor people" all the time) - no legal clause is justified.
Hell, since we talked this topic, anyone can give an example in your own well established country that, a
normal (vs. Li Gang kind of powerful) people, being stopped by police, being saluted by police before any other procedures - that they can slap the police officer's face, and (despite who is right who is wrong) get away with it? I mean, despite their OTHER offences being rightfully delt, do you expect anyone in your country can get away from "assaulting police officer" charge? - Yet this happens like day to day events in China while Chinese security personnels is like fated to be scapegoat.
... So again I conclude, they (the security personnels) don't bother, as long as they
"got you figured out" at first place. And they are freaking pretty good at that.