Why would you even want to walk that line? Is your entitlement and drive for sex so great that you have to compromise your principles? (I'm assuming you have principles about the well being of others who might be taken advantage of.)While "she said she was 18" is utterly inadequate to me I don't think any whiff of a possibility of being underage is a reasonable standard--that means the baby-faced can't have sex. Should I have had to walk away because my wife doesn't look her age? (And, because of the language barrier you couldn't tell very well by talking, either. Also, she's petite enough that almost all her US-bought clothes are from the big girls section, not the women's.) Consider: In the course of one evening I have had one person say I looked too young to be married and another say that I was robbing the cradle. Both individuals were Mormon. (Relevant as they tend to marry young.) If I'm too young and I robbed the cradle doesn't that imply she's way underage?I think grown ass men should walk away if there's even a whiff of possibility of a potential sex partner being underage. It's not like he had no choice. It's not like he had no ethical responsibility.I think age misrepresentation should definitely be a valid defense against these kinds of charges, yes.
I also think 16 years is a better cutoff for age of consent than 18. 18 (or above) is actually pretty rare in the civilized world.
The kind of men who say "she said she was 18" have no moral compass or functional sense of empathy, and don't waste a second worrying about the balance of power there. The Matt Gaetzes of the world are well aware of their power and have no intention of being mindful of it beyond keeping up appearances. We see them.
How about get used to not having sex when you really want to in order to avoid potentially abusing someone?
Why is this even a question? Find some partners that you know for sure are not underage. You too busy looking for reasons to think giving a shit about abuse might be unfair to YOU?