The Knock at the Door

Those of us with the misfortune to live in Golus know what that knock at the door means. It's yet another group of meshulachim from Israel requesting money for a variety of causes. In larger communities, I understand that it's possible to get over a dozen on a sunny Sunday and almost as many in the course of any given week. Fortunately, I live in a small community so we don't see them on a regular basis but rather they come in spurts.
The other advantage of being off the beaten track is that only those who are passionate about their need for collection tzedakah will make the trip out to our community. This means having to deal with far less than folks in the larger community next door (something I occasionally use as a selling point when trying to convince people to move here).
Ah, but you may be asking: why am I portraying these men in a negative light? After all, Chazal tell us that more than the giver does for the taker, the taker does for the giver because of the greatness of the mitzvah of tzedakah that he earns. And this is quite true.
In truth, I have no problem with helping needy causes. I recognize that God has been quite generous and kind with me, far more than my personal performance of miztvos and chesed could ever come close to justifying. One of the prominent commentators on the Aseres Hadibros notes that the underlying reason for the commandment to not envy thine neighbour is because one must always remember that what one has came from God and that therefore one shouldn't try to decide how things should be apportioned in this world. If a man comes to my door with an outstretched hand, should I not see this as an opportunity sent by God? This man's money is in my possession and God gave it to me to give to him so that He could also give me the opportunity of helping my fellow. In this light, these meshulachim should be treasured.
Then there's the educational value. Imagine one's children watching you give tzedakah and treating total strangers with respect. If one wishes to inculcate one's children with the importance of ahavas Yisrael, is there a better way to do it?
So why is it that when I hear the knock at the door my shoulders sag and my lips mutter "not again"?
Perhaps it is my own personal arrogance but I also believe that beggars cannot be choosers, as the old adage goes. I am happy to give generously if need be but I expect that whatever I hand out will be taken with at least a slight smile and "thank you".
Last night, though, that didn't happen. We had three guests from Israel at the door. The first came with a very efficient presentation, had his request all organized and was effusive in his thanks when I handed him the cheque. The second, however, caused me to nearly lose my temper. He was collecting for a Bratzlover yeshiva in the Old City and when I gave him the cheque, he looked at it and announced that if I were only to double the amount, then I would get a blessing from Heaven. My donation to his cause was too small for a blessing?! And when I refused, he continued to argue with me, pointing out how much to my benefit my generosity would be. I noted that the local community also has great needs and I have to think of them first. He pointed out that he had come a long way. I pointed out that I hadn't actually invited him in the first place! Finally, after five minutes of argument he grudgingly took the cheque and left.
Then came the third man who got angry with the amount I gave him (not a small amount). He had been expecting more and seemed to be outraged that he hadn't received it. By this point, I was tired of the whole encounter and told him in no uncertain terms to leave before I took the cheque back and sent him away with nothing.
And today I remain confused. On one hand, I am happy to give. On the other, these people clearly have legitimate needs. Who am I to say no to them? On what authority do I do that? Is there still a blessing on such tzedakah?