Dr Morgan's speech, given on the road to Waitangi, was the latest stop on a tour of venues at which he has attempted to articulate his views on the Treaty.
It was also a platform from which he could repeatedly jibe at Dr Brash, who he called a "hapless" man who "detested" the principles of the treaty.
He said Dr Brash's 2004 speech showed a "confusion (which) reflects a lack of inquiry" which was "sadly lacking for the leader of a major political party".
"The Brash world is one where the only acknowledgement of our identity is our citizenship. This is a tragically one-dimensional view. It is not a case where we are all New Zealanders to the exclusion of anything else.''
Dr Morgan said Maori were accepting a "pittance" of financial compensation in historical settlements signed at a time when the British were numerically vulnerable and compelled to make a deal. He said those who believed settlement of historical grievances ended the Treaty's involvement in New Zealand life were wrong.
Instead, he said it created a platform on which a modern Treaty-based relationship would be built.
For Dr Brash, it was a return to the audience to which he spoke 11 years ago of a "grievance" industry created around the Treaty of Waitangi.
In stark contrast to Dr Morgan, he claimed it made no sense for the most advanced nation in the world at the time to cede so much to a "stone age people".
He described the core of Dr Morgan's views as "nonsense" and rejected his call for compulsory te reo in schools. Instead, he said children should learn more "useful languages" such as Mandarin or Spanish.
"Many of our problems today come from how the treaty has been reinterpreted."
Dr Brash said tino rangitiratanga did not mean what modern "revisionists" had interpreted it to be. He said the original signatories would not have signed a contradictory document.
Former MP Georgina Beyer introduced Dr Morgan and Dr Brash, speaking of the Treaty as being "vexed". She said Dr Brash's speech of 11 years ago "still resonated" in New Zealand.
"It is refreshing to some we have a non-Maori New Zealander who has some idea of what the future of our treaty relationship is going to be. This is what we need to talk about - what is the future going to be?"