You can't control your age just like you can't control your skin colour. Ageism is akin to racism (however an exception for adult only products should be in place)

I don't buy this in the context of advertising. If a company selling do-rag's or haircare products for the hair type found in most black people targeted primarily black Americans would that be racism? No. Not in the malicious sense of the word at least. That should be perfectly within their rights as an organization.

Not to mention that people like Rachel Dolezal and Shaun King probably already pass as black to the algorithm, so they wouldn't be put at a disadvantage by the colour of their skin anyway.

That’s a fair point, but some product just aren’t relevant for people beyond certain age ranges. Age isn’t used to discriminate, it just a cost control by not showing ads to people who won’t react to it anyway.

To some extend all targetted ads are discriminating if we want to go that route.

Without any evidence that they actually turn away non-target customers it seems like a stretch to call age-targeted advertising 'ageism'. Could you perhaps elaborate on this?