A Roman soldier stumbled into a stranger's house and saw a bunch of people drinking red wine.
"What are you drinking there?" - asked the soldier, licking his lips.
"Blood of Jesus" - replied one of the parishioners.
"Who is that Jesus you are talking about?" - the soldier was taken aback.
"Here he is" - said the parishioner and pointed to the icon of baby Jesus.
After stumbling out and wiping vomit off his lips the soldier told everyone he knew that Christians are stealing babies and drinking their blood.
OK, OK, the above conversation is fictional. However, there is sufficient historical evidence that Romans were indeed accusing Christians of stealing babies and drinking their blood. Tertullian, an early Christian author, defended Christians against blood libel in 3rd century AD.
Somewhat later, when Rome turned Christian, the folk tales about Christians had to be quelled, and the blood libel was redirected at Jews.
The tales of foreign people speaking strange language and living amongst "us" and stealing babies persisted, although it never had anything to do with reality. And when Roma people came to Europe they fit the folk tale stereotype just as well as Jews. And to this day there are plenty of idiots in many European countries who propagate the libel, directed to either Romani or Jews.