Atheists/agnostics: do you ever not feel like disillusioning someone about their faith?

I'm not the type of person to talk about religion unless it's brought up, and I won't start saying why I don't believe in a god unless they start saying that I should. But my mother, gosh, well she was forcing some religion at me, and I started saying why I didn't believe in a god, and asking her questions, and her answers got more nonsensical, even to herself, until she didn't say anything, and just kept saying that she wasn't smart enough to explain her beliefs to me, but that other people like her father an professors had given her answers that she found acceptable and that's why she believed. An you know what, just seeing her retreat into a mental hole like that just made me feel really bad. I suddenly saw her as the pathetic woman, who is raising so many kids with an abusive husband. And no, she's not the best mother by a long shot, a terrible mother in some cases. But all she does is work for her family, an take crap, her only comfort is her religion. It's probably her religion that's made her take all this crap, but it's probably her religion that's kept her having some sad pathetic hope that when she dies, her miserable life wont have been wasted. And even hough that's a lie, I didn't want to take it away from her. Especially not, when I saw her clinging to it for her life, irationally when I talked to her. She'd probably kill herself if she realized the truth at this point.