All depends on who you believe: Al Stump, who did spend time with Cobb, and wrote his autobiography; or, Cobb's contemporary biographers, who have rejected most of Stump's accusations, and the two biographies he wrote after Cobb died. They say Stump sensationalized and outright lied about many things, and did so for publicity and profit. Stump was banned from publication in many papers for making things up.
Not saying Cobb was a choir boy, i dont know; but, being an a**hole and being a monster are two, totally different, things.