We can find plenty of answers and comments suggesting that the scriptures or the statements of scriptures are not true.
You are overgeneralizing. This site has about 14,000 answers and I think there are only a dozen or so answers that fit your going against scriptures criteria.
The basis for their answers are from the opinions of historians, archaeologists, secular experts etc.
You are forgetting answers like these that cite one traditional text/commentator speaking against another text/philosophy:
Given the current environment on the site where people are easily offended by the use of mythology tag, it must come as a surprise to a new user as to how the above answer received 32 upvotes. The only reason I can think of is, this was posted in the initial days of the site when the majority of users knew how to keep religion separate from science and voted based on the strength of the arguments made in answers keeping their personal beliefs aside.
And it is important to note that such opinions are not scientific facts.
Do they become scientific facts if the same thing is stated by a guru or an acharya?
E.g., speaking on kings who are supposed to have lived for 1000's of years, Swami Vivekananda said:
However, about the Puranas, I have told you that they are authoritative only in so far as they agree with the Vedas, otherwise not. In the Puranas we find many things which do not agree with the Vedas. As for instance, it is written in the Puranas that some one lived ten thousand years, another twenty thousand years, but in the Vedas we find: शतायुर्वै पुरुषः — "Man lives indeed a hundred years." Which are we to accept in this case? Certainly the Vedas.
As for weapons like Brahmāstra that can be launched out of thin air,
Swami Dayananda Saraswati says:
Question — Is it true what is written in Sanskrit books about the
arts of fire-arms ? Were there guns and muskets in the ancient time ?
Answer — Yes; it is. There were these fire-arms, for they are the
outcome of physical science.
Q — Were they made and used by the influence of gods' incantation?
A — No; it was rules and methods, called the mantras in Sanskrit,
according to which the different missiles and weapons were
manufactured. These mantras are a number of words, which cannot
produce any material object. If a man asserts that a mantra or charm
produces fire, he should be told that it will burn the tongue and
throat of the man who pronounces or mutters that mantra. He goes to
kill his enemy, so to speak, but he is himself destroyed. The truth
is, that the mantra is the secret as in rajmantri, which means the
person who holds the secrets of a state. So a mantra is the knowledge
of certain objects of the world, the application of which afterwards
produces various kinds of things, industries and arts.
Seems like your main issue is not with opinions of historians and secular scholars but with anyone who argues against something stated in Hindu scriptures even if it doesn't agree with reality. In your view, Vedas, Puranas, etc. are beyond reproach, so any answer or comment that challenges them makes you uncomfortable. You are not content with downvoting and attempting to delete such answers but you also want to ban the sources cited in those answers even if they are directly answering a question. This line of thinking is against SE rules. I suggest you read these posts:
In concise, if an answer is directly contradicting the (statements of) scriptures based on expert opinions. How to handle them?
The same way you handle opinions of Vivekananda and Dayananda, by allowing them.