The world is filled with millionaires and billionaires who are publicly known and yet perfectly safe, even though the vast majority of them don't have security guards or anything like that.
Why do you think things would be different for the creator of Bitcoin? The reality is that very few criminals are of the take-hostages-and-murder type in the first place and murdering or stealing from a semi-famous rich person is a surefire way to get caught, especially when Bitcoins are traceable in a way that cash is not. You might as well break in and steal a Picasso painting from some other millionaire.
There are lots of people who want to remain private and unknown; the best (though not guaranteed) way is to not do anything worthy of the public notice. If you do, you should expect some scrutiny. So while I sympathize with Szabo, I don't feel very sorry for him. He pursued his dream of working on cryptocurrency (whether or not he is Satoshi) and this is a perfectly reasonable and predictable consequence of that dream.