Probably every person who cooks has cut themselves while preparing food. Blood can carry many pathogens, so continuing to prepare that food may incorporate those pathogens into the food. Unless it is going to be cooked thoroughly (by that I mean at least 160°F/71°C in the center) it seems prudent that the food should be thrown out, even though it seems a waste.
For food that is going to be served raw, while hydrogen peroxide will probably destroy the blood and any pathogens it may carry, it can also destroy the food or alter its taste, and it may not be 100% successful. And getting the correct H2O2 concentration may be guesswork, at best.
So should we toss the food? It certainly seems the prudent thing to do. Better to waste the food than get sick. Let's assume the blood either got incorporated into the food (not splattered on a nearby surface) and/or the blood was noticed so late that it seems likely that the blood got in to the food. If preparing raw food (salad e.g.), then the blood probably got well mixed with the food, thus making its removal nearly impossible.
Best Answer
There are a couple of things to consider here but it shouldn't be too difficult to cover them all.
If it is just you that is eating it. No problem. You are already exposed to your own pathogens. We've all tasted our own blood. There shouldn't be any real risk here.
If it isn't just you: Stop!
Under no circumstances should you feed me something I have no reasonable reason to suspect is in the food. I am not okay with this even if you do cook it. Are you willing to go into the other room and ask your guests how they feel about human blood in the chicken marinade? If it sounds like an awkward question that you don't want to ask, then throw it out.
That said, there are many foods out there with blood in them. Blood sausage, blood pudding, blood soup and more. I'm not certain of any risks that are peculiar to human blood specifically being consumed. There isn't a lot of research from credible sources out there. I personally would not rely on it being safe just because it can be done safely with pigs blood.
In short, if you cut yourself prepping a salad and don't notice til you've tossed it all together, throw it out. This unequivocally falls under the when in doubt, throw it out clause.