The "Christian" researchers that they use are bias. Very much like the Jesus Seminar. These people only say what people want to hear, that no one is at fault, and we are all blameless.
Historically, Romans, Gentiles, and Hebrews killed Jesus
Acts 4:27 Indeed Herod and Pontius Pilate met together with the Gentiles and the people of Israel in this city to conspire against your holy servant Jesus, whom you anointed.
Now, I will agree that Jesus laid down His own life.
John 10:17-18 The reason my Father loves me is that I lay down my life-only to take it up again. No one takes it from me, but I lay it down of my own accord. I have authority to lay it down and authority to take it up again.
Although, everyone killed Jesus.
I John 2:2 He [Jesus] is the atoning sacrifice for our sins, and not only for ours but also for the sins of the whole world.
But ultimately, God killed Jesus
John 3:16 For God so loved the world that He gave His only begotten Son, that whosoever believes in Him shall not perish but have eternal life.
None of this would have happened if it wasn't for God loving us that He would be willing to give up His Son to die for us.