First of all, by "the rambam" he is referring to Maimonides who lived after most of the Talmud was compiled. Maimonides is one of my least favorite people in history, an arrogant racist who admired Plato and rejected common sense. The Mishneh Torah was actually an interpretation of the Talmud, not a rejection of it. And it replaced the debate in the Talmud with strict legalism, making it even worse than the Talmud. Maimonides had a horrible effect on judaism, and this is who this rabbi admires.
His criticism of Karaite Judaism is that they reject tradition and are anarchists. This is not quite correct. They have their own tradition, they just reject the Talmud as devine.
Finally, his push for unity is wrong. Centralized unity is as bad as individualistic anarchy. The correct balance is in between, as the Mennonites do it. Each community should have its own traditions. Traditions should not be centralized or left to individuals. Traditions should belong to communities.