I've met Rod a couple times, and some good friends of mine know him very well. Based on my (admittedly) limited first hand interaction with him and the much more informed opinion of my our mutual friends who do know him much better than I, I would have to say Rod is not a douche at all.
I think maybe a more accurate term would be poseur
. In other words, he presents himself as someone with higher credentials than he has. His brand is his name (hence the domain name) and his product is to milk the last vestiges of the Roddenberry empire rather than doing something that he can truly call his own. Doing a documentary about his dad surely is not striking out on your own. It's fine to get that out of his system, but if he wants to hang out with sci-fi nerds and present himself as "important" he should have more to show for himself besides a bunch of anecdotes about growing up.
People should realize that Gene himself never wanted to be limited to just Star Trek. He struggled to find another vehicle in the 70s. He kind of fell back on Trek as Plan B. But at least he tried to branch out. I don't think he would have wanted his son to flog old props for a living. He basically embraced the worst qualities of the Roddenberry family, namely the emphasis on direct merchandising (the Lincoln Enterprises thing) and did not try to think or be creative.