I disagree to an extent,
@Zaatar71 .
Typically what is viewed as "attacking a position" is when those who do not agree with that position express their disagreement. But we
should "attack" even our own positions in this way because if they do not stand up to the "attack" they are mot worth holding.
You also need to define "credibility".
For me, any Christian offers a credible argument if they are evaluating a position via Scripture.
People do not need to have a masters degree in theology to evaluate what a person says the Bible teaches against what is actually written in Scripture. Now, it may help when it comes to having studied historical theology and the biblical languages, but it is fairly simple to compare the biblical text against God's words. Often people define "credibility" as being those who have a formal education in theology AND agree with their positions. I believe that type of thinking is flawed (even though I do have a formal education in theology).
I do not believe that Scripture is God's revelation to the religious elite (often the religious elite, the scholars and theologians, are the ones who cannot accept what God has revealed as it falls below their standards and expectations). Instead I believe that Scripture was written for the "common man" of the time of its writing (like fisherman, tax collector, farmers) and has baffled those who think themselves wise for centuries.
Another issue of disagreement is equating "attacking" a position with "doing evil" to the person who holds that position. It is, I believe, the exact opposite in reality. If you look at my belief and point out that it departs from Scripture then you do me a favor rather than an evil.
That said, I have seen arguments against Calvinism that were based on stereotypes and misunderstanding. One of these is the "cosmic child abuse argument".
But having come out of Calvinism, having been a Calvinist, having taught theology, having studied theology, theogical development, and historical theology, I have some insights that those within Calvinism who never went to seminary may overlook (or simply not know). But this helps realizing what is presupposes in a position rather than judging whether those presuppositions are wrong.
Ultimately, however, every Christian has the ability and responsibility to test their faith against the words of God.