One of the instance that is promoted on join-lemmy.org is burggit.moe that is defined as “NSFW & Loli/Shota/Cub friendly”. Loli is legally considered as paedophilia in europe and the US, so even if it’s legal in the country that host the instance, I would suggest to not promote it as an instance to join
You are “wondering”? Your instance should block the instance immediately. It’s in fact a good test. The best setting would be to federate with no one by default.