I think LTG(R) Ulmer generally captured the situation accurately: we know at least generally what toxic leaders are and how to recognize them, we know they exist within the force, and the Army is extremely (perhaps overly) cautious about dealing with them.
From my own experience, I know that toxic leaders abound throughout the Army.
First, I think the Army (and other Services as well) unconsciously cultivates toxic leader traits through some of its formal leadership training programs: the R-Day and Fourth Class System experiences at West Point and other Service academies, the various OCS processes, and Ranger School. In some of these programs, much is made of "Schofield's Dissertation on Discipline," quoted in full below. Practically, Schofield's guidance is honored much more in the breach than in the observance.
Second, I think toxic leaders are tolerated and rewarded because, at least in the short term, they tend to be effective. At various costs to subordinates, they often succeed in satisfying bosses' short-term objectives. Since much of the Army rotates frequently, toxic leaders seem to escape the long-term assessment and accountability for their actions that longer associations might generate.
I think LTG(R) Ulmer correctly assessed the Army's institutional view of toxic leadership when he says, "… The toxic leader phenomenom is a slowly growing organizational cancer that can be tolerated by resilient people for a long time before causing sharp institutional pain. …" and "… Perceived institutional nonchalance about the situation is a serious contradiction of espoused Army values. …" As the old saying goes, "it's mind over matter." With all that's going on in the Army today, the Army doesn't yet mind enough and the troops don't yet matter enough.
Phi Beta Iota: Toxic leadership is not to be confused with unethical or unconstitutional leadership. The focus here is on methods rather than ends. The US Army–and the rest of the US Government–suffer from multiple "leadership" cancers, the most serious being leadership that lacks both intelligence and integrity.