I can't see that anyone here on this thread has "normalized" stealing. Of course guests shouldn't take things without asking. Some hosts suggesting that valuable things be locked up or to only leave enough supplies for the number of guests on a booking and the length of stay isn't saying that stealing or helping oneself to things without asking isn't a big deal or "normal", it's just giving practical suggestions for making theft less likely.
The fact that most people lock their doors when they go out doesn't mean they are normalizing burglary, it just means they are taking precautions to deter it.
As a home-share host myself, I have never locked up anything, nor do I have a lock on my bedroom door. Nor would I home share if it came to me having to do that.
I wouldn't leave my wallet or money or credit cards laying around in shared spaces if I wasn't present, but I have always been careful about that quite apart from having guests- like when my kids were teenagers and there could be lots of their friends hanging out in our home, some of whom I knew well and totally trusted, but others who were unknown to me.
I guess I've been lucky- I've never had any guest steal anything or use anything of mine without asking, aside from maybe borrowing some milk for their cereal when I wasn't around, but they always tell me they did such things and always replace it when they go to the store.
@Andre260