Let's start by assuming that a rational agent might choose as a goal the complete cessation of a particular belief. In that case I'd argue that downvoting patterns, as previously described, are not rational because, rather than having the intended consequence of reducing the likelihood of the expression of that belief, they would in fact simply cause that belief to strengthen and then be expressed elsewhere in alternative echo chambers. In order to establish which of our claims is correct we'd need to empirically observe the propagation of beliefs as a result of downvoting patterns. That would not be an easy thing to do.

However, I would also argue that choosing a goal like 'bring about the complete cessation of a particular belief' would be irrational. Although I accept that once I make that claim the conversation is directed towards very shaky territory. The question of how to choose rational goals is probably impossible to answer definitively.

But I will say that when I claimed that the rational thing to do would be to engage with a disliked belief in a meaningful and polite manner, my assumption was that a rational agent would choose to behave in a way that facilitates growth for both the agent and those with which they engage. Of course, once again, this choice of goal is by no means self-evidently rational.