IMO you have gotten some great responses. I also agree that your question is "open ended" and not really specific as to what you really want to know.
Having said that, I view riding motorcycles as a great hobby. It's also a hobby with some increased risk. But there are tons of risky things we can do. The key for me is to manage that risk by riding smart.....within my limits and the bike's limits. I want to recognize as many "traps" so I can avoid a bad outcome. These traps can be poorly maintained bike, weather, other vehicles, the roads, etc.
If your talking HD's being safe or unsafe from a design standpoint, I would say yes Harley's are safe. Can things fail.........of course. I don't have the data but I would bet serious accidents from a failure of some bike component, where the bike has been reasonably maintained, are statistically way down on the list of primary accident causes.
My question is do you think you would be safe operating a bike? If you approach riding with the attitude that your going to learn about your bike, use good riding techniques (MSF course can teach you some of those), and stay within your limits (ride to ensure there is a tomorrow), you will at least have the safety gods backing you up.