Actually it not a problem untill they try having sex x)

>Cannibals

Symbolism, dude. They drank red wine and ate unfermented bread. Doing so was a representative reminder that the spirit of christ is in you.

So Jesus can enter you but any other guy can't. Explain that shit

You sir, win all my internets.
Made me chuckle.

It's supposed to be because Jesus was the son of God, a perfect human put on Earth. Bear in mind that I am speaking from a religious standpoint here, not a purely scientific one.
Obviously, the Bible's and Jesus' teachings tell that murder and/or consumption of another human being is wrong(Acts 15:20, 'Abstain from blood'). Thus why his statement to eat his flesh and drink his blood is symbolic.
I don't know if you knew this, but (as I previously mentioned) he later explains that the unfermented bread represents his uncorrupted body, and the red wine would represent the blood that would be spilled at his death (MAthew 26:26-28)

Both also serve as a reminder of Jesus' sacrifice, which would serve as a means that all mankind could be forgiven of their sins.
The reason Jesus' sacrafice was considered necessary was because Adam, the first man, commited the first sin, and he was created perfect. Therefore, the only acceptable sacrifice would be another, untainted, perfect man.

Hope that helps explain somewhat. Sorry for the long comment.

It wasn't Adam who committed original sin but Eve, and in certain texts another female named Lilith.
I won't get into original sin though because that argument is too long and I'm too tired.

fight giants, walk on water, cult of cannibals. This started to sound like Skyrim.

Ok what if, hear me out, A guy from the future loved skyrim, Took a time machine back in time to ancient times to see if he could have his own adventure, time machine breaks, BAM writes the bible which is actually a series of skyrim based fan fiction.