'I don't spend all my time calling people out, because it'd be a 24/7 f---ing job,' she says

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It was the Fourth of July tweet heard ’round the world.

This summer, a Twitter troll called Kelly Clarkson fat, and she shut him down with four simple words: “….and still f—ing awesome.” She also garnered universal praise for standing up to body-shaming, but in the new issue of EW (on stands now), cover star Clarkson says she was unaware of the reaction. “I didn’t even know that one went viral until this moment,” she says, laughing.

Clarkson likes to keep in touch with fans and friends on Twitter, so she sees messages like that one (since deleted by the user) regularly. “I don’t spend all my time calling people out, because it’d be a 24/7 f—ing job,” she says. And usually, the comments don’t bother her — she says she has a thick skin she credits to growing up in a small town where everyone knew each other’s business, and to Idolonfox.com, where Clarkson and fellow first-season contestants had to read mean comments about themselves on camera long before Twitter. “[Twitter] is so high school,” Clarkson says. “It’s just the same thing on a bigger scale.”

This one tweet got to her, however. The troll was responding to a Fourth of July tweet in which Clarkson thanked the U.S. armed forces for their service, and Clarkson didn’t appreciate his attempt to ruin a nice moment. She also fired back because she knows her young fans are seeing these comments and listening to these conversations — they tell her as much at meet-and-greets.

“Literally, they’ll say, ‘If they think you’re fat, what do they think about me?’” Clarkson says. “Who cares what they think about you! If you’re unhappy, change something, but if you’re fine, dust it off. That’s where it starts to bother me. Your comment doesn’t bother me, but it might impact other people. I need you to know words are powerful and have weight and gravity to them. So that’s why I do it — but I also love being a smart ass.”

As a singer who’s been subjected to a myriad of (unwanted) opinions about what a star should look like, Clarkson says the blind audition process of The Voice is one of the reasons she decided to join the show as a coach next year. “It’s awesome for it to be based on that raw talent in the beginning,” she says. “I’m very excited to hit the button.”