a false statement. A simple question will quickly destroy the argument.
I like your example of a room full of people and strategic placement of loud voices saying the same thing. We see that all the time, too. On the other hand, the political convention caucus system is an example of how such things work fairly well. Minnesota uses that system in its district and state conventions, and it's great fun for those who understand it.
I'm generally leading one caucus or another at our DFL party district conventions, and have shifted opinion a few times in interesting ways. My caucus at the 2012 Senate District Convention played a role in splitting the convention and denying an endorsement for an incumbent state Senator who had displayed a lack of support for labor interests during his term. No endorsement was agreed to, and he withdrew, despite having gotten the most votes for an endorsement. As it turned out, the candidate I caucused for got the least number of votes. He ended up getting elected to fill that seat, though, through a strong grassroots campaign in the district. He beat the Republican candidate in the General Election 60%-40%.
There is no consensus. There is only majority rule by those who choose to vote in the end in our system of government.