If you want academic discourse about truth, become a philosopher. Activism and power are just as real as trees and language models. Discussing them is discussing the world.
Your concern about motivated reasoning is a valid one – but motivated reasoning is different to persuasive language. If anything, persuasive language highlights the places you should be looking for motivated reasoning (but it also makes it harder to spot, for some people; I don't recommend using persuasive language in your own papers).
I think of it as something like the journalist becoming part of the story. Yes we all have our opinions but to the extent that I can tell what yours are the researcher has become the subject and frankly, that is much less interesting.
Your concern about motivated reasoning is a valid one – but motivated reasoning is different to persuasive language. If anything, persuasive language highlights the places you should be looking for motivated reasoning (but it also makes it harder to spot, for some people; I don't recommend using persuasive language in your own papers).