The foundation of capitalist ideology is a fair exchange of value.
"Fair" is subjective and largely depends on the assessment of needs. Each side is expected to try and fill their own needs as completely as possible. In an imbalance of power, one side is unable to do so and the exchange becomes unfair to the side with less power.
Because we live in a democratic society -- and not, as it were, a capitalist one -- is is understood that the side with more power is SUPPOSED to be the citizens for whom the government nominally speaks, and it is through the government (which represents the people) that that power is manifested.
One manifestation of that power is the minimum wage. It's basically a gigantic collective bargaining agreement.
Why should employers be saddled with that burden as well?
Because the people said so.
Not moot point, because it isn't binary. Yes, technology will and is already pushing employees out, but making labor more expensive is only going to push that faster.
No. Making the technology cheaper will push that faster. Companies that couldn't afford to do it before won't be able to do it with a wage increase (in fact, they'll be less likely to do it because their payroll costs have gone up). Companies that COULD afford to do it will either do it anyway or invest in more skill training for their suddenly more expensive employees.
Of course, companies that already pay their employees 2 or 3 times the minimum wage won't notice any change at all except that they suddenly have a noticeable increase in customers.
Seriously, why would we predict a business owner not buy machines if machines are cheaper than humans?
Because machines can't DO most of the things humans can do. Machines can't replace teachers, paramedics and nurses. They can't replace contractors, construction workers, welders, pipefitters. They can't replace plumbers and electricians. They can't (yet) replace bus drivers, uber drivers, taxi drivers, delivery drivers, forklift drivers and couriers.
If and when machines CAN replace all of those workers, it
won't matter what their wages are.
No human worker can compete with a machine whose hourly rate is effectively zero.
What might happen then, is a whole different can of worms. It's entirely possible that a new economy will form where more and smaller businesses become competitive because a single person can employ automation to reduce his startup costs to almost nothing and let a small army of machines do all of the work. That would make venture capitalism accessible to people who a generation earlier would have just been cogs in the machine. But that would depend on the cost of the machines being relatively low and affordable, which isn't usually the case; ultimately, it's still cheaper to hire and train better employees in many cases than it is to try and buy a machine that can do the same job not-quite-reliably and still needs a technician to supervise it.
it is a burden that the employer can flee from
Not if he wants to stay in business. He still needs to pay SOMEONE to do that job, and if he wants the job done, he's going to have to pay minimum or higher. Automation isn't going to magically save him from having to pay minimum wage; if he has the money to pay $30,000 for a robotic dishwasher that will have to be replaced in a few years anyway and also has a variable cost of ownership (e.g. maintenance, upgrades, technical support, etc) then he might as well just pay somebody $30,000 a year to wash his dishes. At least in this case, the dishwasher can also bus tables, mop the floors, put the chairs away at the end of the day and help the kitchen staff clean up. A dishwashing robot can do none of those things.
The real answer isn't minimum wage increase. The real answer is universal basic income through reverse taxation.
I would agree with this except I don't think a nation like the United States could ever actually provide enough tax revenue to provide an acceptable basic income. I'd be all for it if we could, but the math doesn't seem to work out. From what I can tell, we would need something like $20k to $22k per person to cover costs of housing and food (about $400 per week). Basic income from tax revenues would cost something like $6 trillion per year.
Not saying that's unrealistic, we spend more money than that on stupid shit all the time. I'm saying it's not something that would be sustainable for any length of time, IMO.