He had absolutely no intention of boosting the American economy. If you want to think of things this way "good is good," then know that you are indirectly involved in every good and bad thing that happens in this world, since everything is connected and you can't "disconnect" yourself from being an internal observer.
It doesn't matter if it was his intention or not, good came about, unless you considered the depression a good thing. Also, I realize I'm a part of this world, but I don't have any control over other people and their actions.
He didn't do something good. Something he did brought the need to slaughter his evil, which did good. He had no intention of doing any good. In other words, he was in no way directly responsible for the economy boost. He had indirect ties to it, sure, but he should recieve absolutely no praise for completely indirect results of his hideous actions.
He caused America to get back on its feet again. Whether it was his intention or not, it happened. I am not praising him, merely acknowledging that because of him, America once again showed the world that we were number one.
I personally think that Hitler was a monster; however, we need to understand that without him, many social and economic problems would have continued, and the world might be worse off than it is now. I'm not advocating that we start Hitler Day to celebrate his contributions as a philanthropist.