Against the current US military I dare say that overwhelming numbers would win, against a theoretical future military that is less clear. Moreover the current US military would probably revolt if used to overtly oppress the population, but a more robotized one with humans only required at high levels might not.
The days of sheer numbers being useful are long past in the era of modern warfare.
For example the Battle of Fallujah was fought with Vietnam level tactics. There were about 100 KIA for the US side. The battle could have been fought differently with zero US losses.
The two most famous Socialists in the US right now are probably Bernie Sanders and Ocasio-Cortez. Both are very aggressively anti guns.
"The whole proletariat must be armed at once with muskets, rifles, cannon and ammunition, and the revival of the old-style citizens’ militia, directed against the workers, must be opposed. [...] Under no pretext should arms and ammunition be surrendered; any attempt to disarm the workers must be frustrated, by force if necessary." ~Karl Marx - Address of the Central Committee to the Communist League
Source: https://www.marxists.org/archive/marx/works/1847/communist-l...
That is not true of Bernie Sanders [0]. He has moved to some degree towards favoring more gun control laws than he used to, but he is by no means more anti-gun than most mainstream Democrats.
[0] https://www.npr.org/sections/itsallpolitics/2015/06/24/41718...
Actual hard left - the kind that actually believes in Marx and revolutions - is not a hive mind, but it is true that it tends to be a lot more acceptive of grassroots violence, and things that enable it (like guns). Which is not all that surprising, given the history of the movement.
Look up Redneck Revolt or Socialist Rifle Association to see what I'm talking about.
To elaborate: Hillary Clinton's 2016 platform included increasing the inheritance tax, and she's about as centrist as Democrats get these days. The inheritance tax is redistributive. Did any Democrats come out against her position? https://www.forbes.com/sites/robertwood/2016/09/23/hillary-c...
https://en.wikipedia.org/wiki/Redistribution_of_income_and_w... says: "Redistribution of income and redistribution of wealth are respectively the transfer of income and of wealth (including physical property) from some individuals to others by means of a social mechanism such as taxation, charity, welfare, public services, land reform, monetary policies, confiscation, divorce or tort law."
But at least part of their definition of includes that they have the chance to increase their position, which is incompatible with tax/regulation at the extreme: if everyone has their incomes set in stone by the government, there is no chance to change in status.
But losing all low-level jobs to robots, notably, removes that chance. For different reasons than the liberal (who dislikes it for the centralization of wealth/power, and the extreme polarization of wealth distribution), conservatives would intuitively be against it for the denial of opportunity across the board
Tldr: everyone hates being poor/homeless, and too many people being homeless will cause a revolt regardless of their individual political leanings.
There are many useful things that aren't (or won't be) viable as jobs because they pay too little or too sporadically to sustain yourself, however, they do provide enough to increase your revenue and status, and give a feeling of opportunity - if you'd have the basics provided in some other way.
Applied to UBI’s case, the baseline of $0 has been “lifted” to say $1500; wouldn’t that just cause the market to increase prices proportionally, until $1500 is effectively the same as $0? Specifically, those baseline goods/services where that $1500 targets?
I would imagine luxury goods wouldn’t change much, as those spending in the area won’t change their spending behavior significantly with a fresh $1500; but a poorer community certainly would, and I would expect the market to match
One aspect that would change is the rental market. We would expect the landlords to try and capture much of that money. However, the big impact of UBI on rent is that it decouples the residental areas from the industrial areas; if you don't need to live where the jobs are and can credibly leave for a place where rents are cheaper, then some people will do so and that puts a limit on the rents.
As you state, small poor communities would feel a significant impact; however, in their case the main effect would be that they would become subsidized by the other parts of the society - much of the UBI they get would be spent on goods coming in from outside; their local market won't impact the price of a bottle of Coca Cola or a bag of potatoes, it's coming "from outside" anyway.
The cost of local services, on the other hand, would become much more spread out - if currently the cost for many services clusters around a single point (often close to minimum wage) because everybody needs a job so they do that service even if they don't want to; and everybody needs to eat, so they have to charge a reasonable amount even if they would be doing it as a hobby; In an UBI world you'd expect the cost of services to spread out widely so that services that are pleasant and interesting (for the provider) are cheaper than now, and services that suck for the workers become more expensive, as the workers now have a choice.
To your question, it is easier to break a tank than to operate one. Anti-tank weapons are cheaper than tanks, and range down to well-timed Molotov cocktails [0].
[0] https://www.quora.com/How-can-a-Molotov-cocktail-destroy-a-t...
In the US at least, there's 1+ gun for every man, woman, and child. Even if the elite class is backed by the entire US military, there's something to be said for overwhelming force of numbers.