Wow, you guys have been busy...
I'm not going to delve into this debate, but I would just like to point something out as I have now observed it in more than one post.
If something is wrong, it is wrong. It is proven to be as such using the evidences. However, repeatedly trying to prove something 'guilty by association' where even the suggested link is vague and ambiguous is not more than a logical fallacy. Iirc it is what is referred to as reductio ad Hitlerum.
Secondly, there are certain acts that take one out of Islam. I totally agree with you that takfeer is something overused by some people, perhaps more so with some groups, and that isis are also guilty of this. However, certain beliefs or actions can bring one out of the fold of Islam (eg claiming divinity).
Thirdly, idk a thing about Majid Nawaz. If he does good, this ought to be acknowledged - but likewise, we ought to acknowledge any bad that is from him and assess which of the two overpower our view of him. If someone does something good or praiseworthy, it does not necessitate that everything done by the person must be correct.
That's all I wanted to mention, from a neutral perspective in this discussion
When you say 'man-made', this has connotations of fabrication. The discussion of whether ahaadeeth are reliable or not is a long one, requiring both parties to discuss in detail, not really suited for the purposes of this thread.
For now, suffice it to say that your presented argument is not beyond rebuttal and much can be said on such a topic.