I feel like the tumblr user asking why it's necessary to tell people not to eat blood meal must have forgotten they're on tumblr. The whole site is just smut curated by the generation that turned eating tide pods into a meme.
It makes sense to clarify. There are many dishes made with blood, black pudding and blood sausage comes to mind.
Also it's good to let people know because dogs absolutely love that shit and you have to be careful to keep it out of areas dogs can get at it.
I worked in a green house and one customer's dog dug up an entire tree she planted to get at the blood meal she put in the bottom of the hole. Dog was okay, but needed to stay at the vets a few days to monitor the vomiting and their iron levels.
My first thought was if it could be rehydrated and used as a more easily acquired prop blood, as opposed to pig's blood.
If animal blood is acceptable then I'm not really sure why stealing from a blood bank would be a primary course of action in the first place...