No, they should not have forced to allow all comers to air an opinion (not that that would necessarily have been a bad thing), but the situation you've given is

No, they should not have forced to allow all comers to air an opinion (not that that would necessarily have been a bad thing), but the situation you've given is one of a time with healthy competition between a plurality of media outlets. If any one of them a) was a monopoly in its sector, and b) was also providing a platform initially to anyone that wanted one, then I would agree with the comparison. Considering the Patreon fuss and now Mastercard's "human rights committee", it's not only "build your own website", it's rapidly moving towards "build your own bank". It's not realistic.