I did not reply to this comment the first time I saw it but I have been wiggling my mind around it for a while. My first gut feeling it's that it all comes down to the belief that the fight for rights is a conflict at its core.
For most social fighters the notion that there are winners and losers in how society works is a given. From that standpoint you'll have people who want to take revenge over "current winners", or to even reverse the winnings so everyone is poorer but somewhat in a closer level to each other. Logic would beg us to look at social change as a non-zero sum game: everybody must win. Since most social interactions are downright inventions very little stops us from making the most exotic solutions works other than making people agree with each other. When people start to get a communitarian mindset they no longer start to work for "everyone" they simply redefine what "everyone" means to fit the small population that they believe to represent.
This is a flaw that you can find in any kind of open democracy, where people are only allowed to be for or against something. Selecting options without an ounce of critical thinking is ridiculous and blurs the value of the choice that is being made. When people think they are fundamentally right sometimes they stop applying critical thinking to their own agendas. Smart and nuanced opinions are not valued in a society where the loudness and indignation are the only kind of revolt.