Why was bestiality such a big deal that they had to mention it in the bible so many times.
Giordano: Well, first of all, bestiality is in no way related to homosexuality, any more than it's connected to heterosexuality. Bestiality doesn't involve consenting adults and would be considered by most people as cruelty to animals.
But you're right, the Bible mentions bestiality in the Torah, namely, Exodus, Leviticus and Deuteronomy. Why did God see the need to warn against it at all? It's not likely any of the Israelites were committing bestiality, so why was it mentioned? There's a reason for it and all the other restrictions mentioned in these Bible books. People who don't understand the reason, however, shouldn't be using these verses to apply to people today. If Jesus and the apostles didn't use these OT verses to apply in the first century -- they would certainly have more insight on the purpose behind these verses than we would -- who are we to take them and start beating people over the head with them?
As the apostle wrote at 2 Peter 3:16: "[Paul's] letters contain some things that are hard to understand, which ignorant and unstable people distort, as they do the other Scriptures, to their own destruction.