Could Roddenberry's FU personality have been a carryover from his days as a street cop? Justman was astonished when he found out Roddenberry smoked weed.
I was wondering that too. Either that or his time in the military.
It sounds like he just wasn't very good at playing the political game in Hollywood, and just wanted to push through his ideas regardless of how many feelings got hurt along the way.
Of course he also spent quite
a lot of time writing scripts for other shows before Trek (and trying to create new shows), so I can see how he could have become pretty bitter and fed up with the studios by that point.
And he did
have a lot of early success in Hollywood, so I'm sure that probably went to his head as well.