To some people, this may seem stupid, but too me it is really just a civil protest, not unlike blocking a road.
Brazilian example: a few months ago, truckers (who are mostly in favor of our proto-fascist president Bolsonaro) blocked highways country-wide, while threatening (physically!) others to join or people who tried to pass through their blocks, and got no big response from police. The joke at the time was that the best way to get police to act was call them saying that schoolteachers were conducting a peaceful protest and wait a few minutes for them to come with full force, SWAT-style.
An unarmed, native blockade over a pipeline being rammed through their territory gets an over-the-top response, from heavily militarized federal police.