I don't think that's what's going on here. The claim that

1) one should act ethically, and that
2) acting ethically includes the vague-but-intuitive class of "not being a dick"

goes against the general trend here of saying that,

a) Morality is non-reductionist or otherwise just a fancy term for preferences [1], and
b) You should only care about the consequences your actions cause.

Summarizing one's justification here as "I don't want to be a dick" is therefore not a simplification[2], but a repudiation of what seems to be "the rationalist answer" here. That's why I said it gave off a vibe of, "but, but, rationalists can be nice too! We'll make an exception for that!"

[1] or whatever the heck EY's point was with his meta-ethics series
[2] though it's defensible as such a simplication for cases where being a dick is immediately visible to others, like I mentioned in another response here