Is it bad to use villains as an inspiration?

I would have to say no. I don't see anything wrong with having a villain as an inspiration. You just need to be aware of what about that villain inspires you. Hitler was considered to be very smart and had a strong political grasp. He had a very different view of how to change the world, and it was because of the past he had. I don't personally believe anybody is bad, just some people are lead into the wrong direction. Just know when you're going to far with your goals and know when to ease out and all should be ok. And remember in Hitler's mind, he was not murderer, he thought of himself as a purifier. He was just trying to create the ultimate race. But we are a society of diversity and that didn't really go over too well with the rest of the world. So if you want to take his leadership skills as an inspiration I would totally agree it's ok. Just as long as we don't take his idea of purifying the human race as an inspiration. But if you're concerned about your popularity at school, I wouldn't really tell too many people that Hitler inspires you.