You have an interesting way of conversating. I figure I'll throw my own "experience" in. I've met unemployed people absolutely content with their life, producing nothing of any value to the economy. I've also met unemployed people that are unbearably miserable.
I think the basis for their mental states are entirely related to how they see work. Some people, such as yourself, believe only productivity can justify their existence. Indeed, some people have suicidal thoughts simply from the idea of being unproductive. It's no mystery to me which forces contribute to this kind of thinking. On the other hand you have people who think productivity is sinful, destructive, perhaps even counter-intuitive to our lives. These are the folk that are usually miserable with their job.
You also have a subsect of working people who dislike their job not because of the environmental mayhem it causes, but because they lack meaning. What is a burger flipping job but charity? Lost time one can never get back. Some people are willing to take this sort of social "hazing" where they essentially work at cost just to be able to say they have a job. But some people see this as either unacceptable or unreliable in terms of boosting overall productivity. They prefer either shortcuts or more sophisticated motivators, call it what you will.
This I think explains the diverse reactions to UBI. While most educated people have no issue with it, there will always be groups, educated or not, that have different principles in life.
The purpose of UBI, I should like to think, is to prevent unnecessary suffering. For someone that cannot work safely or reliably, society is better off investing in their life itself. Society has little use for dead people, but a living person has future potential. Just as we hesitate to "pull the plug" on the terminally ill because there could be a cure any moment, society hesitates to condemn peopls to die when at any moment that person could be capable of re-entering the workforce.
I think you're also failing to consider charity, citizen science initiatives and other "unemployed" activities that still yield tremendous social value. Having a job is nice and I couldn't be prouder of you for navigating the workforce as you have. But to say I consider your life more valuable than, say, someone paralyzed below the neck would be a total lie. I don't know what knowledge that person has that you do not, therefore I cannot intelligently prioritize one of your lives. If you have to sacrifice part of your savings so someone 2,000 miles away you'll never meet won't die, most people will be in favor of it. You can say you're being forced, but I would rather say you aren't being forced to live in a dangerous society. You're free from being surrounded by poor, untrustworthy folks who will tell you all kinds of stories to get a few bucks.
Wouldn't you rather be able to trust people?