The first step in looking for a respected theologian who can propose this view is to define how we know a theologian is respected, and I suggest a minimum requirement is that he or she is a theologian who has written works that are cited by his or her peers; a theologian is also likely to teach theology in a tertiary environment, but perhaps this is not so necessary for our purposes. Such a theologian would need to disbelieve most of the scientific evidence that we have about dinosaurs, including that a great many dinosaur species were quite small - even though popular imagination focusses on the few very large examples - and that the last of the dinosaurs died out some sixty five million years ago. The theologians we are looking for would therefore be proponents of Young Earth Creationism.
The author of this blogspot is a Young Earth Creationist, although the absence of a biography suggests he or she is not yet considered a respected theologian. This blog contains theological errors, even citing Genesis 3:14-25 to prove that Noah's bloodline hadn’t been contaminated by the fallen angels' and the Nephilim's genetic tinkering, when the nearest brief reference that could be interpreted in this way is at Genesis 6:9 (
These are the generations of Noah: Noah was a just man and perfect in his generations, and Noah walked with God.) The blog also assumes the nephilim survived the Flood, against God's clear intention when he called down the Flood.
Allen Austin says that nephilim altered DNA to create dinosaurs. Austin has written and self-published (Xulon Press) two books about religion (The Middle of the Earth and The Messianic Temple) but provides no information about his academic status. I can find no online citations of his work by any theologians.
Rev. Daniel F. Owsley has written and self-published (Booktango) several books, including one called Dinosaurs Weren't Created By God, in which he states that the book was not written for Catholics or Protestants, but for Christians who know they are victorious or want to be. Owsley appears to be a minister of religion but, in spite of the large number of self-published books, I can find no citations of them by any well-known theologians.
I am not personally aware of any respected theologians who offer the possibility that dinosaurs were on the earth at about the same time as nephilim and were the offspring of demon angels, and an online search has come up blank. This is not to say that there is no respected theologian who holds this view. The nearest my search has come is Rev. Daniel F. Owsley, who has some credentials, as a minister of religion, and appears to believe that nephilim were responsible for the dinosaurs.