Seems highly one sided to me.
The law in the UK states.
"Any Fixed blade or non-fixed blade with a lnegth in excess of three inches is automaticly considered an offensive weapon unless the defendant can prove otherwise".
Essentially, a fixed blade, or non-fixed blade greater than 3 inches is assumed to be "offensive" and you will be arrested if found carrying one unless you can prove you have a legitimate reason for carrying it. Any non-fixed blade under 3 inches, like the smaller swiss army knife for example is NOT assumed to be an offensive weapon, and you can only be arrested if using it in an offensive manner, or in conjunction with anything that effects your state of mind like drink or drugs.
Now one could take the view that the mans faith legitimises his carrying of a fixed blade, its dodgy ground though.
Even better: change the law so that people are not charged with carrying an inanimate object, but rather for what they do with said object. If the knife is in his pocket and he is not bothering anyone, he should be left alone.