The dilemma... (just rambling!!)
There is no point answering or offering the justification to Taylor, because he is not looking for one or needs one. Even if I did offer him a justification, it would not bother or enhance his approach in anyway.
On the other hand, if there is someone else - other than Taylor - that I need to offer the justification to, then the problem is that I do not have a 'formal justification'. I really do not and cannot state that there is a norm that now needs to be followed or based on which the theory holds good. Because if I do so, I'd be undermining the basic Constitutive theory which I intend to uphold. I therefore need to justify the factors that need to be recognised and permitted to have a role, without themselves becoming norms or bound by norms.
Who then would be such a person, who could use Taylor's theory - albeit with some drawbacks that need to be addressed? The closest I found is Willard Quine...
Rorty!!