SG comes across to me as more mature than the "average" 18 year-old. Because he said one comment that was kind of ignorant, does not mean that he deserves to have this "age-ist" back-lash. Having said that (and this is me speaking as ME, not as a moderator), I find some of SG's phrasing a bit predictable and quaint, as Fidelia said, "things I used to say or think when I was your age". When I was 18, 20, 22, etc. I used to HATE when people said this kind of stuff to me!
HOWEVER - regarding the statement about fat or skinny not caring about themselves enough to care about a relationship with SG:
I read that and thought "Well that's HIS loss. It's not MY problem." There are some people who might feel compelled to "educate" SG in order to fight against oppression and marginalization, and that's all good, but it's not my thing. I tend to be lazy.