Do you mean for a save file that you already turned it on for? The way it works is that once you enable it for a save file, that's it, that save is purged, even if you disable the setting again.
I mostly made it that way because due to exactly what that setting does, it's not something anyone who would actually be using it would want to toggle on and off generally. It's not a setting I would recommend for many people, even those who don't want to see lesbian scenes. I may change it so that it doesn't permanantly affect saves in the next update though, since I mostly made it this way to kinda parody the absurdity of the setting.
Sounds like something is suuuper broken. Sadly that's not something I can fix for just a save file, but here's a console command that will manually switch the setting to be off. You can google how to enable the console in Renpy if you don't already know how. It's fairly easy.
Open the console and run the below exactly as written. It's case sensitive. (Ignore the name. I still think this setting is dumb lol)
persistent.AndYetSeverelyDisabledLesbians = False
Worth remembering though that this won't affect any saves that are already "purged". You can tell if a save is "purged" because if you hover over it in the load menu, it'll say "This isn't a very spicy save" or something.