Then it is one specific place still

That you must go to advance tbe main quest, regardless of faction. Every player must go there.

It makes the Legion eviler then Enclave

When was it stated at cottonwood cove?

Don’t know what got Nazis got to do with anything. But did the enclave use children for this?

Just to clarify, there is no reference to child sex slaves at Cottonwood Cove. The daughter in the family kept there (Sammy) is young, but clearly uses the adult NPC model. Not the child one.

This is not to say the Legion doesn't do that. It would not exactly come as a shock given how dark their culture is.

So her being young, regardless of how adult she may look, is still a child sex slave

That's now how that works.

Basically the Legion have not shown themselves as a very diverse(healthy diverse) and accepting(that doesn't involve killing) group so this form of slavery is likely high. They literally view humans as a resource and commodity instead of individuals.

I did have my suspicions that I was being slightly mislead because I was getting the impression I was blatantly told in-game because I feel like I would've remembered underage sex slaves in Cottonwood Cove. Implied maybe. Such as "The new slave girls are quite beautiful".

With my experience with mysogony, "girls" is a common way sexists refer to women of similar age group to themselves to put down women's abilities and achievments as ignorant, uneducated, incapable, or inept at a task or job. So the Legion men are either devaluing the women even more by referring to women as "girls"(which is likely the case) or it is literally meaning the socially associated use for girls for someone young or underaged. Especially since education in the Legion I doubt is very high for slave soldiers either.

“Young enough to breed”. Cannon Runner

That doesn’t sound pedo at all. If she was an adult then she would have left her abusive father. She is still a child.

Legion worse

This is supported by nothing in-universe. It's speculation.

Human breeding age goes til late 40s. Canyon Runner states that Sammy is young enough to breed, but her mother is not (full context). Sammy is an adult NPC. You're using the fact that she is still living with her family to claim she must be a child, and the use of an adult NPC model is incorrect? Nothing in-game supports this.

To reiterate what was said before: the Legion more than likely does sexually abuse children, since it's outright stated that Sallow reinforces harsh beliefs in their culture to promote rapid population growth. But in this case you're making up evidence for this where there is none.