What reasons does Atticus give the children not to play the Boo Radley game?

Atticus told the children they were tormenting Boo, that he had a right to his privacy. He told the children to stop making fun of him..... stop putting his life on display, and to quit making a scene in front of the entire neighborhood. Atticus explained and reprimanded the children because it was the right thing to do.

“Son,” he said to Jem, “I’m going to tell you something and tell you one time: stop tormenting that man. That goes for the other two of you.” What Mr. Radley did was his own business. If he wanted to come out, he would. If he wanted to stay inside his own house he had the right to stay inside free from the attentions of inquisitive children, which was a mild term for the likes of us. How would we like it if Atticus barged in on us without knocking, when we were in our rooms at night? We were, in effect, doing the same thing to Mr. Radley. What Mr. Radley did might seem peculiar to us, but it did not seem peculiar to him. Furthermore, had it never occurred to us that the civil way to communicate with another being was by the front door instead of a side window? Lastly, we were to stay away from that house until we were invited there, we were not to play an asinine game he had seen us playing or make fun of anybody on this street or in this town

“We weren’t makin‘ fun of him, we weren’t laughin’ at him,” said Jem, “we were just-”

“So that was what you were doing, wasn’t it?” “Makin‘ fun of him?” “No,” said Atticus, “putting his life’s history on display for the edification of the neighborhood.”

Jem seemed to swell a little. “I didn’t say we were doin‘ that, I didn’t say it!”

Atticus grinned dryly. “You just told me,” he said. “You stop this nonsense right now, every one of you.” Jem gaped at him. “You want to be a lawyer, don’t you?” Our father’s mouth was suspiciously firm, as if he were trying to hold it in line. Jem decided there was no point in quibbling, and was silent. When Atticus went inside the house to retrieve a file he had forgotten to take to work that morning, Jem finally realized that he had been done in by the oldest lawyer’s trick on record. He waited a respectful distance from the front steps, watched Atticus leave the house and walk toward town. When Atticus was out of earshot Jem yelled after him: “I thought I wanted to be a lawyer but I ain’t so sure now!”