Sourced, objective rebuttals you say. Let’s take a look at their issues under “methodology”:
“Amnesty’s methodology section is opaque and inconsistent with internationally recognized fact-finding standards.” [0]
The source in that passage leads to a book
* Best Practices for Human Rights and Humanitarian NGO Fact-Finding (Nijhoff Law Specials) by Gerald M. Steinberg, Anne Herzberg, Jordan Berman (2012) Paperback*
Who is the lead author, Gerald Steinberg? It would appear to be the president of NGO monitor. (Ann herzberg is also on their staff) [1]
Unfortunately I don’t have the ability to exhaustively research all of their sources, but this is hardly credible.
[0] https://www.amazon.co.uk/Practices-Humanitarian-Fact-Finding...