If these women are younger than them, I think the judgement can be safely categorised as jealousy. The fact that you're picking partners younger than them makes them feel like they're not good enough, which is why they are upset. That doesn't make you selfish - you don't exist to make others feel good.
I’m around the same age group as the above commenter described, and I can confidently say “not being supportive of dating someone significantly younger than yourself” at our age is looked frown upon. We usually joke about “lol i can’t imagine having anything common with 21 year old self, and as a self respecting person, i wouldn’t date one either”.
I think it’s a cultural thing, and personally I wouldn’t judge two of-age people making their own decisions. Really depends on your group dynamics and groupthink.
Also, not every co-ed friendship is rooted in jealousy or sexual desires.
