Based on your line of thinking, people should be fleeing Belgium in huge numbers. Belgium is in the EU and has land borders with Germany, Luxembourg, the Netherlands and France. Germany is not far off in taxes, but France is at 29.1%, Luxembourg at 31%, the Netherlands at 30.4%. Anyone with Belgian citizenship can work and live in any of these countries without having to apply for any visa or work permit. (so far that also applies to the UK, over the channel, but given Brexit I ignored it)
Most Belgians speak French or Dutch, so language should not stop them.
Yet, despite these rather significant monetary incentives to even move across the border, within a short driving distance from their current location, to countries with the same language, there is somehow not a massive amount of Belgians fleeing the country.
Note that this is tax burden for an average tax payer. Not marginal rates paid by the very few.
In other words: Sure, people act on incentives, but unsurprisingly peoples decisions about where to live are not only down to a few percentage points of taxation. Some will move, many won't, and yes, that is something to take into account when setting tax policies.
1. Government is necessary since some things are best run by public services and without a for-profit motive.
2. What are these things?
3. How much money should be raised to properly run these things?
4. What is the optimum tax rate/policy to achieve this goal?
My framing allows people to say 1. in response, if it is able to specify 2., and if it can then determine 3 and 4.
What it doesn't allow people to do is say "the state is entitled to as much in taxation as it can get away with, because the state also builds roads and hospitals" ('You didn't build that'), or "the state is entitled to use taxation as a proxy for creating equality of outcome" ('This is Class Warfare').
I don’t understand the point of your first paragraph. It’s a caricature of people you call the Left. I have never seen anyone anywhere paint taxation as an unalloyed good in and of itself. Can I suggest that instead of talking in terms of Left/Right that some other dialog be used? This is why I framed things the way I did. There’s not mention of Left or Right. It’s just questions that get at the heart of what being a society means.
I doubt you can large numbers of the Left saying what you claim. Specifically that the reason for wanting to increase taxes is to get rid of wealth inequality. I have heard people say things to the effect that beyond a certain point the wealthy can afford to pay more taxes in order to fund some programs. These things are nuanced and it's not helpful to reduce everything to a slogan.
I find offering the option quite appealing, in the sense that it would hold government strictly to account if it annoys sufficiently large minorities to warrant large splits.
But what the people opposing taxes often tends to forget is that if you want to argue that society should be organized in a fully voluntary way, then the rest of society don't owe you access to any of their public services either if you're not prepared to agree to their terms for interacting with you.
If someone is ok with taking the consequences of that, then, hey, let them, but in my experience the moment you point out the likely consequences, there is a tendency to start crying about how unfair it would be when other people want to exercise their freedoms to refuse to deal with someone not prepared to pay their share. In other words, most of this boils down to wanting to be free to pick and choose how they interact with wider society, without wanting the rest of society to be able to pick and choose how to interact with them.
This is a very silly statement. The small fraction of people who leave has increased a little bit in size.