I'm a little stumped that this happens quite a lot on pages that has absolutely nothing sexual about them or in them.
I would venture to say that there is about a 1 in 20 chance that they actually got it right but then it is in the text and something sexual was said or referred to but even then it is mostly innocent or could be understood incorrectly. I cannot recall a situation where I would say that their robot was 100% spot on because all pages that displays ads are properly vetted before ads are actually shown on them.
Most pages do however have some photos with people depicted in them and it is probably this? Perhaps their AI does not really have that much intelligence? I'm puzzled to what could actually be triggering this? The AI probably thinks the photos are nude photos or have something sexual about them?