Regarding argument in good faith:

If you’re looking at the arguments made by any kind of small insular group – which can be small either because it’s fringey or because there are very few people with the expertise/credentials/whatever to get involved – you can safely assume that, right or wrong, most of those arguments represent the actual thoughts and sentiments of the people making them.  When you’re a member of a small insular group, there are not a lot of reasons to dissemble.  Generally the group members’ interest lie in spreading the group’s ideas, which involves making the best arguments that they know for those ideas, which are…the things they actually believe.  (In theory you could have something where an evil and Machiavellian group makes palatable-sounding arguments for things that will actually benefit group members at everyone else’s expense, but…that brand of conscious evil Machiavellianism is not common, it’s especially not common amongst people who think that being identifiably weird in discourse is a good plan, and in general the burden of proof here is a very heavy one.)

If you’re looking at arguments made by members of a large and popular group, especially one that’s dominant within a wider social sphere, argument-made-in-bad-faith becomes a much more salient issue.  People will say things they don’t believe in order to gain status within the group, because “gaining status within the group” comes with meaningful benefits even for those who aren’t already invested.  Similarly, the group is likely to contain a lot more people who are only kinda-sorta believers, whose membership came about through going-with-the-flow or even through inheritance, and those people will subvert the group’s ideology by making specious arguments in order to get what they personally want.  Even outsiders can gesture at the group’s ideology to call in discursive “air support,” if the group has broad enough sway.  And, of course, actual Machiavellian types are going to be drawn like flies to high-status groups (and ideologies) that can give them power rather than marginalizing them.

This is a structural feature of society, and it works independent of the content of any particular ideological argument.