The habit of basing belief in what the person says on the person's credibility goes to many undesirable directions. One extreme has been that of accepting the cosmology of Jesus because he was supposedly sinless, while rejecting the cosmology we see from science because scientists are supposedly sinners.
I can't begin to list all reasons why this is wrong.
Carter was a good person, but his policies did not work. Clinton was not such a good person, but his policies did work. There are any number of kind, compassionate people who go completely astray and fall for all kinds of rackets. That they are kind, compassionate people, does not make them any less wrong. Meanwhile there are many not so good people in all sorts of places, from academia to business to media, who honestly study what's going on around them and come up with useful conclusions.
How many personally admirable people espouse Islam? How many personally admirable people took part in Communism? My grandmother was an amazing person, and she was a Soviet Communist. That they are good people does not mean that they are right. And the same is the case with Jesus.
There are some who accept Jesus as the source of all their moral instruction, and there are others who see Jesus as a false prophet, a conman or a decoy. How about, just, he was wrong? All sorts of good people find themselves wrong about something. I can give any number of examples of good people being wrong about something, even someone as wise as the Dalai Lama or as knowledgeable as Einstein or Niels Bohr.
Was Jesus (if there was Jesus) really a good person? Well that depends on whom you ask. There have been all sorts of people in the history of the world who suffered or sacrificed themselves for others. And most of these people did not aspire to be anyone's lord and savior or to claim ownership over people's lives or to be the ruler of the world.
Yes, I went to Christianity voluntarily; and yes I found much wisdom there. If you want to laugh, laugh. But truth is not a matter of personal credibility. It is a matter of the correctness of one's claims. And that is entirely unrelated to personality and entirely unrelated to what people are as human beings.
The biggest problem with Christianity is its claim that everything that is not Jesus is Satan. Don't tell that to the Buddhist group I attend. I've found in these people admirable qualities, such as compassion, kindness, dedication and interest in everybody's well-being. Buddhism pre-exists Christianity by 600 years. I've also seen admirable qualities in people who follow Hinduism; and Hinduism pre-exists Christianity by much more.
Is there any relation, positive or negative, between one's personality and the truthfulness of one's claims or observations? Freud, Nietzche, Ayn Rand, John Rockefeller, Henry Ford, Kierkegaard, Bill Clinton and many other major contributors were deeply flawed individuals. Whereas there are any number of good-natured people who have been following Islamic Jihadism, Communism, right-wing Christianity, white supremacism, and any number of other errant paths. If anything, the person who stands a chance at coming up with a real discovery is the person who thinks differently from people around him. And that is bound to cause interpersonal conflict in such a person's life.
The standard is therefore the truthfulness of one's claims, not the personal qualities. This is especially the case in matters as significant as one's cosmology. Whether or not the scientists are sinners, they make testable claims that another person, sinful or not, can either verify or refute. Whereas many Biblical or Quranic claims, whatever the character of their authors, are not only not testable. Many of them are also manifestly wrong.
Different natures will be found in any given place. What matters is what these natures are doing and on what they are right. Clearly basing judgment on personal credibility is a disaster. Base it on verifiability, base it on sensibility, but do not base it on something that totally is irrelevant to the subject.