is the ego the villain in Bhagavad Gita?

You could put it that way. Nobody wanted to give in, all had to have their way. And worst of all is that once the movement towards war began all realized that they were just pawns in a game that had long been in the making. Once things got to be so far along Arjuna realized that he had to do what he had to do or back down and face the consequences of not being able to live up to the job, a horrible job at that but one that had to be done. Not too much different than that which many of our modern day leaders have to face. Make terrible decision that effect millions if not billions of humans.

The Ego is always the main villain in every spiritual journey/struggle.

It is the Ego that binds us in this world of life and death, right and wrong, good and bad, etc. A bondage in endless dualistic struggles. By overcoming the Ego, we free ourselves of such bondage and "return" to the Self.

Not at all. Bhagavat Gita denies ego altogether.

What? You didn't read it at all did you? Making it up as you go along....

no, children and skepticism are