In order for two parties to engage in a fruitful debate, it must be theoretically possible for one side's claim to reveal itself as a better conclusion given the available information and, for this to happen, both sides must speak the same evidentiary language. If the two sides do not ground their competing claims in the same type of evidence, the entire debate would consist of them talking past each other. For instance, imagine pitting someone who believes one's favorite color is best determined by how often he wears it against a someone who believes one's favorite color is best determined by whatever he says it is debate the claim "Marshall's favorite color is blue." Each side refutes the validity of the other's evidentiary language so a debate regarding which conclusion is best supported by the evidence would be pointless as they deeply disagree about what even constitutes as evidence. The only potentially worthwhile debate with this pair regarding favorite colors would revolve around the more fundamental question of what evidentiary language is best suited for determining one's favorite color in the first place.
The same absurdity arises in debates in which materialists and theists argue over metaphysical claims like the existence of God or the basis of morality. The materialists speak the evidentiary language of logic and science whereas the theists speak the evidentiary language of faith and feelings. If both sides stuck to their respective languages, a debate would be impossible. It would reach an immediate impasse as each side's arguments fail to challenge the other's justifications. However, during such debates, the theists typically attempt to utilize the evidentiary language of logic and science to bolster their arguments and deconstruct those of the materialists. This approach never bodes well for them since it is impossible to logically derive the existence of a metaphysical realm from the material or prove the existence of any specific non-material thing scientifically. By using the evidentiary language of logic and science, theists implicitly concede to the materialists' methods of justification and consequently grant them an upper hand in the debate rather than simply expressing the fact that their view is not justified for them through such means.
The motivation for employing this odd, counterproductive tactic seems to ultimately stem from modern society's growing reliance on logic and science as methods of determining what is true and untrue. Because many people now find scientific and logical justifications more compelling than those rooted in faith, theist debaters often appeal to the former manner of determination in an effort to win over the conflicted souls unsatisfied with the idea of only using faith to justify their worldview. These people yearn for some form of logical justification, however fallacious and incomplete, to seemingly support the view they wish to hold more confidently. Members of this group fail to understand that faith exists only in the absence of adequate logical justification and that the trepidation they feel holding a view founded entirely on faith is precisely why faith is so often presented as challenge. This is especially true in today's society which primarily speaks the evidentiary language of the materialists.
When theists appeal to materialist reasoning, they do a disservice to their own epistemology and worldview by pretending like their belief in the metaphysical can possibly be supported by an evidentiary language that, by definition, excludes the possibility of faith. Since positing the existence of any non-material entity exclusively requires faith, the thestic position cannot possibly be any further justified by any appeals to logic or what has been proven through science. Citing what can only, by definition, be incomplete logic based arguments as additional justifications to faith for a theistic worldview completely misses the point that such a worldview requires logically unjustified faith in the first place and detracts from the challenge of living one's life without desiring logical justifications for what one can only believe through faith alone.