I think there is a distinction to made here.

Threads such as "Scientific Proof of God", "Evolution is a hoax", hell even the "Flat Earth" thread - although these threads are running in to the hundreds of pages, there is still discussion going on. People are quoting and directly replying to each other's points, even if some of those points are batshit insane.

In the spam mega-threads in Bitcoin and Altcoin boards, there is very rarely any discussion. It's just bounty spammers churning out the same generic meaningless posts to reach their requirements. The problem is that these bounty spammers will take over a thread almost immediately and any actual discussion that was going on in the first page or two is completely drowned out and lost. By page 5 onwards, it's pretty much 99% bounty spam guaranteed.