You are so arrogant as to believe that something YOU don’t accept to be true is therefore UNJUSTIFIED.
But anyone can say that about anything.
I do not accept atheism.
THEREFORE atheism is unjustified.
Q.E.D.
I would dispute the claim it is UNDEMONSTRATED, noting that often
1 atheists misdefine “demonstration"
2 atheists reject cogent demonstrations by acts of will
1 Theism is entirely epistemically JUSTIFIED
2 No theist NEEDS to have recourse do DEMONSTRATION as the basis of their JUSTIFICATION, and few do
3 Theism is demonstrable and demonstrated, although this isn’t very important