It is creepy for any person to target a much younger person based specifically on their age above all else. There is only one reason to do that - because you enjoy controlling someone you perceive as likely to be weaker than you.
That says nothing at all about whether it is possible for age gap relationships to be based on love and mutual respect or for them to be between people who are happy and want the same things.
What the op, I suspect, is now freaked out by is that her BF's statement seems to imply that it is legitimate and desirable for men to do this - target younger women because of their age. That this is normal and just the way men are.
Agree with doin it is the youth that is attractive to this type of man, not because of any crap about breeding but because they are attracted to the idea of control and not equality. They are essentially afraid of women the men who deliberately seek out young women. And that IS creepy.
The friend may just have happened to have really liked a particular person who happened to be that age, I don't know, but the idea that it is acceptable to deliberately seek out much younger women because they are much younger is what is creepy.
I also don't get the 'don't make a big deal of it' stuff. It is not a big deal, it is a new BF of a matter of months not a long otherwise happy marriage of a number of years. This kind of stuff is exactly why you should dump someone early on - now is the time he is on his best behaviour, good reason to suspect worse will come if it continues.