My opinion is that the situation with your father is not analogous to the Bush=Hitler phenomena.
It is useful to remember that what one gets from the left is more often their emotions, not their thoughts. In most cases (at least in my experience), "Bush is as bad as Hitler" is not the result of a thought process. It is, rather, a rationalization for an intense hatred of anyone that dares to pronounce moral judgment.
What generates this hatred? Remember, many on the left are victims of the educational comprachico's campaign to cripple their conceptual ability. As Miss Rand explains in her article, “The Comprachicos”, many of them are, quite literally, unable to function on a conceptual level. Their arrested mental development induces a fundamental fear, because they realize, at least intuitively, that they have no way to deal with reality. Complementing this fear is an overwhelming hostility against anyone who does not seem to be as mentally impaired as they are, and especially toward anyone who presumes to pronounce judgment.
(Of course, the degree of mental impairment varies tremendously from victim to victim; I am speaking of the extreme cases, the ones I believe are today’s hard-core leftists.)
How do they deal with this fear and hostility? Many resort to the rationalizations provided by their professors.
In her article, "Philosophical Detection", Miss Rand observes that evil philosophies are systems of rationalizations, and many popular catch-phrases are rationalizations for underlying emotions that one does not wish to face or acknowledge. Well, the comprachicos of the American educational system have turned out two generations of students who are unable to think and are brimming with ugly emotions that require cover.
I believe this explains the bizarre phenomena, very common today, of the leftists who assert the most extreme, even outrageous notions with absolute certainty ( "Bush is Hitler" is but one example), but, when questioned, cannot summon any reasons to support or explain their position. They only know how to emote; they never developed the ability to think. When I question their positions, what I usually hear in response is a stream of insults, cheap smears and various forms of ad hominem. That is when I know I am not dealing with a mind, but rather its crippled remains.
Whatever errors may exist in your father's thinking, I don't think it compares to these people.