I never said he makes things up. I said he doesn't get his angels/human hybrid beliefs from consistent exegesis of scripture. If you look at the first link Philip posted, you'll see from where Mr. Heiser gets his beliefs. Legends and extra biblical writings, mixed with eisegesis of scripture
So did Paul and Jude and Peter.
Just to clarify... Paul, Jude, and Peter say absolutely nothing about angel/human hybrids.
For me, the two fatal flaws in the angel/human hybrid theory are:
1. As Rick points out, the angel/hybrid theory is not based on Scripture. It is based on extrascriptural traditions that came into being during the intertestamental period which is thousands of years after the time of Enoch or Noah. So these traditions are not even close to contemporary with the historical events of Genesis 6. And as I have pointed out elsewhere, there are portions of these extrascriptural books (like Enoch) that directly contradict Scripture.
2. The angel/human hybrid theory is based on the presumption that the phrase "sons of God" in Scripture refers to fallen angels or even Satan himself. Again, we've beat this dead horse with a stick, but there is not a single place in Scripture that refers to fallen angels or Satan as "sons of God". And this premise flies in the face of what Jesus says about being a child of God in John 8.
That said, I have a lot of respect for Michael Heiser, and my disagreement with him on the angel/hybrid theory does not mean that I do not appreciate his knowledge and scholarship. Which is why I actively search out Heiser's views on a number of topics.
And even where I disagree with Heiser, I do not think he "makes things up".