No place is inherently safe; every space ends up having predatory people in it.
Well-run communities/organizations/schools/whatever have things in place for dealing with this. And, from time to time, abusers hurt people, and the communities actually use the things they have in place for dealing with abuse.
And they will be able to tell you what those things are.
And if the community has been around for a years, they will be able to tell you about instances in which that has happened. (In general terms; they don’t have to (and usually shouldn’t) reveal identifying details).
If a school or business or something gives a training on harassment, and they can’t tell you what’s happened in the past when abuse has happened, and they only say “we take that very seriously”, it’s a major red flag.
If a community/school/whatever tells you that abuse can’t happen there because of how great people are, or how much training there is, or anything like that – that’s an even bigger red flag.
The safest communities are those that recognize that no space is safe all the time, and that it’s always necessary to be on the lookout for abuse.