I recently came across the theory that the Flood was…

I recently came across the theory that the Flood was God’s way of purifying the human bloodline tainted by the Nephalim, with Noah and his family being the last family on earth of pure human blood. This being necessary to protect the bloodline that eventually leads to Jesus.

Reference:
“There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.”
‭‭Genesis‬ ‭6:4‬ ‭KJV‬‬

Honestly, I did not even know about Nephalim until I came across this theory after a read through Genesis. The theory seems very speculative to me, which can be dangerous if not clearly presented as only theory.

Can anyone elaborate on this theory? Maybe both for and against would be interesting to see.