I disagree. I don't think they're justified. Not to the extent that they'll easily outright condemn the only basic cable TV network that still cares to broadcast anime with/without a merchandise tie-in. And when people say it's not enough whether those openings and closings are available on home video, digital download or somewhere on the internet, where do you draw the line with how entitled people have the right to be?
Honestly, I don't see people condemning Toonami for this decision, or at least not that badly. I'm sure people were upset about not getting any full openings and I do think that's understandable, but I haven't really seen any outbursts that negative. If they don't air the openings for Attack on Titan, assuming that they'll get it, then I could see the reaction being more negative and I could understand that too. Those openings are hugely popular, especially the first one, and even with the themes being available on home video releases and digital download, they would want to see them on the TV airings because of how popular and successful both the show and openings have been. I doubt that it would affect the ratings since Attack on Titan is still a really popular show, but it would be an understandable disappointment about not getting to see the full openings along with the show.
While I can understand why people are bothered by the situation with the opening and ending themes, it hasn't really gotten to the point where it's overwhelmingly negative and preventing me from enjoying the block. It's too bad that we didn't get at least the full opening to Space Dandy for the world premiere, but that isn't so much of a deal breaker for me compared to say the actual content of the shows they air. Granted, at this point, they only shows on the lineup that I genuinely like right now are One Piece and FLCL, although I'll give Space Dandy a few more episodes to see if it does more for me besides having really great animation.