Sign that an organization does not have a good safety culture:
Focusing on reassuring you that the organization does not have predators and harassers, instead of focusing on what to do when those types of people pop up.
Because those types of people always will pop up. If you think you can somehow magically ward them all away, you're lying to yourself. But damn you can sure attract a lot more of them if you don't deal with the ones who've already set up shop in your org.
I'm mostly thinking about LARPs writing this, but I'm sure it applies to broad, broad swathes of organizations.
tl;dr: An organizer trying hard to convince prospective members that they've never had harassment problems and never will makes me automatically assume they've had tons of harassment problems that have just been ignored.