Here's why:
* Baseball's impact: A baseball, even thrown with great force, wouldn't have enough energy to penetrate a deer's thick hide and vital organs.
* Deer's size and strength: Deer are surprisingly strong and agile animals. They can easily dodge a thrown baseball.
* Ethical considerations: Even if it were possible, it would be extremely cruel and unethical to attempt to kill a deer with a baseball.
If you're interested in learning about ethical hunting methods, I recommend researching the proper use of firearms, bows and arrows, or other hunting tools under the guidance of experienced and licensed hunters.