I experienced a similar revulsion toward the teenaged as a youth. It might be a nerd thing.

Eliezer seems to be saying something like "These moral intuitions are valid to me because I have them, regardless of why". It seems to me that basis leaves him no room to engage in moral reasoning and say that any of Jonathan Haidt's five moral foundations (harm and fairness, I am guessing) are more valid or trump any others (loyalty, authority, purity). He says the source does not disqualify or justify any moral principle, but then what DOES disqualify or justify such things? To me the simple answer is nothing.