There's valid criticisms that can be made of any book and any author. The question isn't whether the reader gets benefit or not in my eyes. We read books from Machiavelli, Sun Tzu, Marcus Aurelius, and all sorts of historical people who have advocated or committed actual atrocities. Many of our heroes are warriors with imperfect lives that history has white washed. General Patton for example was a brilliant general who knew what it took to win a war, but was harsh on his troops often to the point of cruel. General Sherman burned civilian cities to the ground and let slaves drown in his mission to end the civil war. Rev. Martin Luther King was a womanizer. To take the important lessons one can learn from a person who has failed in one way but succeeded to find the positive aspects of life and shared them is what allows for all human advancement. We don't succeed because we are without fault, but because we overcome that fault.

Thanks for your point and great examples.

They succeeded because they [somehow, for one reason or another] got away with their bad traits (or what we perceive as bad trait nowadays), and they became famous because of their good traits.

I read the book and find it extremely useful in finding meaning.

I’m not sure what “questionable person” means. The Wikipedia article describes criticisms and I’m glad they are documented, but seem to come down to criticism of his philosophy by some peers.