“How can you argue against a miracle from God???”
Therein lies the rub. Even if this blood miracle happened exactly as they believe, they can’t know if it’s a miracle from God or the result of Satanic/occultic power. It’s easy to see how people are fooled by the lawless one “whose coming is after the working of Satan with all power and signs and lying wonders.”
Also, we can’t forget that in Exodus, Pharaoh’s magicians or sorcerers were able to copy some of the signs God gave Moses.
Often people see things and mistakenly think they perceive them correctly, Eve being the most famous example.
“And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.” (Gen 3:6)
I often wonder what Eve saw that made her believe the tree was good for food. Regardless, what she saw did not mean what she thought it meant.