This all comes down to the "Gish Gallop" problem. It is easy to vomit out disinformation and lies. Anyone attempting to poison the well can do so much faster than you can refute their lies with facts and well-reasoned argument.
When the other party is acting in bad faith all it takes is some money and time to subvert platforms with paid shills that all network with each other and mix disinfo into seemingly normal content streams. This allows the shills to build credibility.
Good luck dealing with that. You can reply with all the well-reasoned arguments you want but when 500 of the shill's friends bury your reply (and mass-report you) no one will see your message so correctness becomes a moot point... not that people have enough free time to read and consider every well-reasoned argument when they come across an issue to begin with. If you tried that you'd need more than 24 hours in a day.
This is only a problem because platforms weigh any post equal to any other, but for their rudimentary upvote systems. If posts with actual backing behind its claims were weighed more positively, they would gain more prominence and status, and people spewing out unsupported info could get filtered out as simply noise.