Hi gavra-at-work.
You were replying to a specific point. One you created and bent to fit what you had to say. lol
You can go on and on, but the point is if someone comes to your door or is collecting tzedaka in any manner, and you are wondering if they are legit; give. Dont hold back.
It is a mitzva to give and the heavens act accordingly.
The way you said what you did, is dangerous. Had someone NOT been a fraud, even though you suspected it, and you refrained from giving. THAT is a transgressing; a big one.
Please dont poskin for people to gamble on chas vshalom making a transgression in tzedaka. Give two dollars or some change. Aight? lol
I am sure there are other proofs, but I quickly found that the Aruch Hashulchan states that if you suspect a person may be a fraud in collecting clothing, you can investigate it because the person can wait.
BUT..if you suspect a person may be a fraud who is requesting food, do not investigate it.
Also, if you are ‘CERTAIN’ the person is a fraud, as I state earlier, obviously, do not give, which is also stated in the Aruch HaShulchan.
Naturally, I am open to you finding a proof for holding back tzedaka because you have a feeling the person is a fraud. You are free to create a new scenario so your view fits, too.