Someone I know of made a comment recently about when Jesus turned over the tables of the money changers in the temple. There seems to be some misunderstandings running around about what was really happening there. So here's the impression that I get.
In Jesus time, the temple was not the kind of place that it was envisioned to be when it was built. When it was built, it was the holy place of Jewish worship. Jews from all over the world were required to come to the temple once a year and offer a sacrifice. For some, the sacrifice was a bull or a ram. Obviously, more expensive sacrifices were required from those who could afford them. Those who could not afford a sheep were required to sacrifice a dove or pigeon. Another requirement was that the animal be perfect, that is to say, it could have no blemishes, birth defects or diseases.
From the beginning of the temple, there were those who did not have their own animals to bring to the temple to sacrifice. A carpenter for instance didn't raise sheep or doves and therefore likely would have to buy an animal for the sacrifice. Day laborers (otherwise known as the poor) also often didn't have any livestock of their own and were required to buy an animal. Also, people from far away likely lived in a kingdom or area with a different kind of currency than was accepted at the temple, so money changers were employed in the same way they are now in international airports.
What began to happen as time wore on in the temple was what happens in many situations when you leave a ruling establishment in charge for a long period. They started taking advantage of the situation. Money changers started to charge exorbitant fees to transfer into the local currency. Some even say that those in charge of inspecting the animals began to say that the animals were not free of blemishes, requiring the person to buy an animal from the temple staff for the sacrifice. In some cases, they even say that the person's old unclean animal was even resold in the same market as a clean animal.
The net result of all this as in most cases of corruption was the disenfranchisement of the poor. The poor are the most likely to be affected by any corruption since they cannot afford to buy what they may be forced to buy. Later in the same discourse, Jesus addresses this by mentioning the widow's two copper coins and that she had given all she had. The highlight is when we understand that those coins were equal to 1/128th of a denarius which was a days wage. As you can see, it was a minuscule amount of money, yet it was all she had.
So it was not simply the selling of items in the temple that Jesus detested for such sales were a necessity to provide the people with sacrifices. Neither was it the changing of money because that was also a necessary part of temple business. Instead, it was the dishonesty, the usury and the taking advantage of the people who came to worship. The Jewish system of religion required a blood sacrifice for the atonement of sins and it was the "paid religious professionals" of the "church" who were blocking the people from attaining the forgiveness they sought. This is why Jesus called them "thieves" or "robbers" depending on your translation.