You're assuming, rather uncharitably, that people in favor of "private entities cannot be compelled to host the speech of others" only support that point of vie

You're assuming, rather uncharitably, that people in favor of "private entities cannot be compelled to host the speech of others" only support that point of view because it serves other political stances they hold, rather than as a general principle. A site is free to ban all left-wing groups, all right-wing groups, all centrist groups, all groups with an 'e' in their names, all hate groups, or all of the above. Others are free to react to those bans accordingly, and choose whether to associate/support/host the site or not.