When challenged on this, they tend to defend this strategy by claiming that many, if not most people, do actually subscribe to the belief in question for the very reasons that they are attacking.
Of course, most people might well believe something for weak or misguided reasons -- or indeed, often for no reasons at all. But I do not see how this has any relevance to the truth or falsity of a more nuanced stance on the belief in question.
For example, many people believe that evolutionary theory holds that we humans descended directly from apes, or even monkeys. But would attacking such a notion and showing how implausible it is, have any implications for the actual mainstream evolution theory? Obviously not, since attacking such a wrongheaded notion of evolution doesn't touch the idea that both humans and apes evolved from a common ancestor (humans didn't evolve from apes!). But this type of attacking of the more naïve stances taken on a belief happens constantly, for example when attacking the notion of an afterlife.
If we want to show a belief is foolish, we don't achieve this by attacking and ridiculing the weakest reasons and/or evidence, even though many people might be convinced by such weak reasons/evidence. Rather we should seek out the strongest reasons or evidence and attempt to show that it is lacking.
I think the main goal when people argue is to get back-slapped by their supporters and increase their status and prestige amongst them. But I also think they themselves become convinced that they have genuinely confronted the best reasons and evidence. People actually self-deceive themselves that they have genuinely engaged with the more powerful arguments and defeated them. This seems to be pretty much universal, even within the academic community.