Blip, me old chum, why do you persist in trying to reason with the unreasonable?
If some dodgy chap, who almost certainly knows full well his bike is stolen even if he wasn't personally responsible for nicking it, has your bike, don't go and
talk to him! What do you think he's going to say? "Oh, sorry, old man - my mistake. Do have back your velocipede and I sincerely apologise for the confusion." No, he's going to tell you to f- off and back it up with violence. Stick a sod off big D-lock round your bike, walk inside McDonalds and refuse to engage at all until the police arrive, other than to apologise and assure him that if it is indeed your mistake you'll buy him a coffee. End of.
As to the rest of the floating dreg-ends of society - yes, some cyclists will be crap. Some drivers will be useless cretins. Some kids will be on suspiciously nice looking bikes. But why does it always have to be you who approaches them to intervene? Why do you always try to engage these people in dialogue? You must know by now it's a fruitless exercise. And, like Karen says, making yourself that unpopular in a local area is a big mistake.