I suppose dodging and burning in a traditional darkroom is cheating? Same with cropping and enlarging? I suppose people who use film shouldn't push or pull their exposures. In addition, everyone should use the same film stock, because using an oversaturated film stock would be cheating.
Want to know a secret? Your camera processes each and every photo you take, making adjustments, just like Photoshop might make. And if you shoot RAW, you absolutely need something (like Photoshop) to process it, unless you want a terrible image.
Just like adding a filter to your lens, or changing the ISO, or any other tweak you can do "in camera," Photoshop is a tool to be used however the photographer (read: Artist) wishes to use it. If you choose not to use it, because it's "cheating" that's your choice. But that would be like trying to build a house without a hammer. It's certainly possible, but it's going to be much harder to accomplish, and the result will be terrible.