very weird. Maybe a new thing?

In general, it is weird to assume that the younger party is being taken advantage of. The younger party might, among other things, be taking advantage of the older party's status in society. This goes for both genders. Note that taking advantage of a partner's status is not equivalent to taking advantage of the partner himself or herself.

And saying that an older man is shallow for dating younger women is equivalent to saying that younger women do not have depth and interesting quirkiness to them, so it is actually devaluing younger women to say that. Not protecting but devaluing. The exact opposite.