I think the idea of marketplace of ideas is that an idea loses by being unpopular, not by another idea persuading large institutions to ban it. Your interpreta

I think the idea of marketplace of ideas is that an idea loses by being unpopular, not by another idea persuading large institutions to ban it. Your interpretation, that persuading a large institution to ban opposition ideas is winning, and being banned is losing, is entirely consistent with getting rid of the 1st amendment.