So, I have this friend who has an amazing bat. With this bat, he hits things and gets all his anger out.

This simply means that the bat could easily slam against anything and not break.

I'll borrow that bat from him.

For you.

And we'll go on a rampage.

...(referring to the last comment) not saying that you're infuriated about it or anything, hey, it could be fun. I know it would make me feel good.