Hahaha. Whose rationality? Yours? Everybody thinks their own views are rational. If they didn't, then they wouldn't hold those views.
What you're describing here is ethnocentrism. What about eating insects? Eating insects is a very logical and rational thing to do, so I hope you enjoyed your maggot cereal for breakfast and your tarantula sandwich for lunch. Wait that's icky? Well sorry, that rationality police says you must eat your insects.
What of people who want to live a certain way becasue they rationally chose that? People who rationally want to be Catholic or Buddhist? Whose world view ultimately wins out that they get to enforce it on everyone else? And when that happens revolution happens. You cannot obtain a world government through overreach and dictatorial processes. You will always have rebellion. People must be free to live as they chose. Otherwise *poof* there goes your world government. And that mean allowing people to live in a way that you disagree with, or even hate.
The issue with the first argument is that people thinking their arguments are rational means nothing. Yes, everyone thinks their views are rational but many, many aren't, There is a difference between believing you are rational and being able to rationally, ethically and morally justify your actions. That's where most of those viewpoints collapse.
The first paragraph is silly. Cannibalism and religion are not equatable to eating insects. Insects are a food choice and a healthy source of protein. Nobody could rationally force you to eat something you didn't want to purely out of 'rationality'. It is rational to eat to stay alive, how you do that is up to you and has no impact on another individual. Cannibalism, for example does.
Your third paragraph is an oxymoron. One cannot rationally be religious. As with your original sentence, one can think they are being rational by being theistic but one is not. The argument is that religion is simply one of a vast multitude of outdated 'isms' that will continue to fall by the wayside as humanity advances [and human history shows this to be true]. Nobody is being 'forced' to not be religious, it will simply become so [as is happening world-wide right now].
Your second part of that paragraph is quite aggressive, for want of a better way of wording it. You seem to view a utopian system as one gained through force, or revolution and whose ideals must be enforced. I think Trek hints at a reformed world where the evils of today are gone [greed, hate, hunger, poverty etc] and where religion likely does still exist but in severely limited pockets and this is perfectly acceptable.
I think you are reflective of some of the arguments made against Trek's utopian society that, somehow, it would involve repression. If that society is based on rationality then you would be free to do as you wish and diversity would thrive more than it does now...but a multitude of things that are 'wrong' and can be rationally demonstrated as being 'wrong', will be forbidden. You can't cry for a racist because his freedom to be racist is denied. He is the irrational one.
But forcing people into a certain paradigm of what they should be is the antithesis of freedom. I can easily see a world government as being possible. But not by forcing people into what I want them to be. Saying, "oh, if only people were rational, then we could have peace on earth." is like wishing people had three arms so we could get more work done. It doesn't matter, becasue we don't. Humans are an irrational, emotional, diverse bunch. And creating a world government doesn't have to be a "wish-upon-a-star, if-only, if-only" scenario. By allowing people to live their lives it is easier for people to get along even when we disagree
You cannot have a one-world government where every part of the planet does what they want. People would be free to do as they wish: so long as it was ethical, moral and rationally justifiable. Differing opinions and rationality are two different things and I think you are confusing that. Badly.
What will the slow death of religion do? What does religion do now the prevents us from a Magical One World of Unity?
In terms of Star Trek you are forgetting that humanity reached a united state for BEFORE there were transporters or replicators. In today's terms we have a huge abundance of resources, yet the people in power make more money by keeping the status quo, so things don't change.
It is divisive nonsense. It places emphasis on an existence apart from this one. It is dogmatic. It encourages people to be happy with not knowing. You cannot have multiple faiths on claiming to be right and expect, fundamentally, that to work properly. I could go on and on. The death of religion would usher in a new period of though on life, on existence and on the world in general. You also, again, are being overly aggressive in your statements: religion isn't purely responsible for us not having a united earth, it merely plays a part.
I remember Trek's history but in the context of countries I was discussing how those technologies would further change Earth and our view on the nation.
And you can be free to live in a community of people with those same beliefs as you, with a legal system that is centered around your beliefs. Or you can be free to travel to other communities of people with differing belief systems than you. See how that works? I'm not forcing my beliefs on you, and you don't force your beliefs on me. And if I find myself in some place that has beliefs I don't agree with, I leave.
That isn't how things work though. If your beliefs is that every blue person is inferior and should be shot, you deserve to have your beliefs challenged and changed. If the objective is to create an enlightened, united Earth, then certain beliefs will have to die because they are simply irrational and 'wrong' regardless of how uncomfortable for some people that may be.
It is NEVER that simple, becasue humans aren't that simple.
That reminds me of the X-Files episode where Mulder gets wishes from a genie. He wishes for world peace and POOF everyone in the world but him is gone. If Christ, Muhammad, Gandhi couldn't create world peace what make you think that you can? And what army will follow you as you impose your world view of rationality on others?
Those three names you mention are laughable. 'Jesus' was fictional and never existed, Muhammad was a tyrant who couldn't get his own village to listen to him and needed to spread his message through violence and Gandhi was a racist monster as well. I can't stress enough how weak it makes your argument look.
I also loathe the defeatist 'logic' you are using. "If x couldn't do it, why bother?" which is utterly, utterly contrary to progress.