It's interesting how, in S3, they present the Xindi as being from a planet where 6 separate sentient species coexisted and developed, no prob. 'Course the Avians became extinct, but that wasn't due to other species' acts, prejudices or selecting one group over another, so far as I recall.
If the order of the episodes is reversed, and Dear Doctor
comes after, say, The Shipment
, then Archer, etc. could and should have said, "Well, the Xindi managed to have more than one sentient species grow and develop without it turning into civilization. Why the hell can't the Valakians and the Menk do that, particularly as an offshoot of overcoming this medical crisis?"
Hell, send Xindi councilors in, to show 'em how it's done.