But for determining truth, both sides are wrong here.
Dunning-Kruger is bad, but so is credentialism and appeal to authority.
Many people with PhD's have had Dunning-Kruger. Someone else mentioned Ben Carson being great at neurosurgery, but not politics.
A PhD doesn't make you infallible.
I am saying this as someone who is taking graduate-level courses and will be pursuing my PhD. When I'm correct, it's not because my future PhD causes reality to magically conform to my opinions - it's because I rigorously looked at the evidence, logic, and formed my own conclusion that better aligns with reality.