Here is my experience: I have used this instruction my self for one side, I could see my bumper hole for a clip bent a little bit, but it won't crack at all. Certainly, like other people said it won't break anything. Bumper material is like elastic and flexible plastic.
Here is my method to remove grilles.
Just push clip up and pull toward you one clip at a time
Just press and pull toward you one clip at a time
Hope this work and you can use above method with confidence as well. Don't be afraid to pull with above method.
Before and After pics: