Newman is allowed an opinion, you have opinions.
What about when this;
has been done (already) and the results of the examination be not as supportive of a few 'dogma' in particular?
Sorry mister, or sister, or whoever you are -- you simply cannot get away with accusing others of having merely and only "personal opinions" (if aspect of "mere" was included though unstated within your screed) when opinions contrary to your own and Newman's are based upon evidence as it more truly is (compared to how it's often massaged/manipulated/cherry picked by RCC apologists) when it is your own opinion and Newman's also that things are as commonly advertised (advertised by promoters of various and sundry RCC claims towards their own [Roman Catholic's] alleged unique 'authority' to have introduced doctrine and dogma not found within the texts of Holy Writ, and not present either within the first few centuries of existence of Christianity.
Newman, and a few of those in his own era all but invented that kind of idea, adopting that while still attempting to successfully assert "unchanging", and "as instituted by Christ" etc., at the same time.
Singular papacy, as that is known by the Church of Rome? What's not pure invention about it is distortion of what was more properly "instituted" among the early centuries 'Church'.
Marionism to the extents that has been expanded from beginnings of need for recognition of her (Mary) being the virgin prophesied that would give birth to Messiah? Pure inventions overlaid truths serving to much distort and introduce significant change (theologically speaking) to the underlying truths.
We (myself and millions of others who have examined these things --in detail--) could go on somewhat further, but for now, that is enough.
It is not from standpoint of "personal opinion" alone that there is opposition to particular doctrines and dogma of the RCC (if but limited to particular key aspects of those same).
In this, your (failure of a hunting dog) dog is barking right back at you, each time it yaps while running around the same (and wrong) "tree"...
Your comment: “We (myself and millions of others who have examined these things —in detail—) could go on somewhat further, but for now, that is enough.”
“you simply cannot get away with accusing others of having merely and only “personal opinions””
You are certainly entitled to believe whatever your heart desires (freedom of religion) and there are 30,000 different protestant religions so you have lots of options. It is still your personal opinion that may be shared with many others. Please explain how it is not a personal opinion?
What is your authority other than personal opinion that you understand the Truth of the teachings of Jesus, the Apostles and their successors?
Newman was an example of a non Catholic that went back and studied the teachings of the Catholic Church each century and determined them to be truthful. Yes it was his personal opinion and he acted on his research by converting to Catholicism.