To me this is how the scenario breaks down in various components
Intent - their intent, by my own moral compass, is good. If I had my 'druthers the legal system would somewhat allow for this kind of thing, although they would still be heavily scrutinized if they shot someone, obviously
Legality - It is legal to do what they are doing, but they are obviously on a very dangerous and thin line by talking about baiting, etc.
Benefit - Who knows, this is hard to say. Will the thieves stop trying to target people, or will they just avoid the people strutting around with their chest out?
Cost - The cost could be huge to any of these people if they DO use a firearm for anything that could remotely be considered vigilantism.
All in all, a very stupid idea in this society, which is a shame, since their intention is not bad even if their execution is misguided.