It bothers me too. But in Bellamy's defense, I can be a bit forgiving of those in the late 1800s who were socialists, because there was not practical experience with socialism at that time, and I can see why it appeared to make sense back then when compared to the sometimes harsh realities of industrial-era capitalism.
Of course, now that the world has had 150 years of real experience with the horrors of actual socialism in practice, there is no longer an excuse for ignoring the clear superiority and comparative humanity of free-market capitalism.
Also, at least back then American socialists appeared to be patriots. Can you imagine any modern American progressive composing something like the Pledge of Allegiance today?
But they would have been familiar with the French Revolution, wouldn't they? Wasn't it a socialist experiment?
I do agree that cultural and moral relativism would prevent today's leftists from writing anything even remotely similar to the Pledge.