I can’t remember the exact, pithy phrasing - but there’s a sentiment expressed sometimes in activist work that I find helpful: “We wish you were with us before, but we are so happy you’re here now - there’s much work to do.”

A meditation, perhaps - shared because you will likely encounter this situation often over the coming years and maybe it will help you as it helped me.

Analogies are weak. We should discuss and express concern for everything that happens, and not give up part way through and cease highlighting/flagging anything at all, simply because of repetition, or the vague emotion of "you should have known already". The parent did know. Everybody did know. It's irrelevant to the specific topic.

I.e. the genre of negative response you've given is distracting, accomplishes nothing helpful, and, sadly, is very common.