It is an honor to meet an Angel, an honor that I am perhaps unworthy to receive. Very few Nephilim can say they have been in the presence of an Angel. Though the Angels gave us their blood as well as the Mortal Instruments and the runes that we etch into our bodies so that we could defeat the demons that had been able to pass into the realm of humans, they leave us mostly to ourselves. I'm afraid I have never heard of the Grigori.
I'm so sorry to hear of the massacre and suffering of the Angels. It's awful to hear of such a thing. All the Angels have ever done for humanity is give us the ability to defend ourselves against the demons. This does not seem like a crime to me.