By not giving 1% of your wealth to Africa you're disadvantaging a billion people to protect the wealth of one. It's not a disadvantage to someone that they're not getting a part of somebody else's wealth; we're not born with some divine right to other people's money.
The talk of guillotines is completely out of place by the way: the French revolution was not a bunch of peasants guillotining the rich out of envy; they were guillotining the royal family, for taxing them too much!
That is rather reductionist. At the time, the landed gentry, nobility and the church were the rich people in France. The middle class guillotined the rich because they were the ones paying all the taxes while the actual wealthy were not paying any taxes at all. I'm sure you can see the overlap with the present day sentiment.
https://citizentruth.org/the-secret-deal-that-formed-the-us-...
It's just the strangest thing to me.
Additionally, even amongst the general population, let alone startup founders, the number of people with wealth in excess of $100m is tiny. Numbers are hard to come by but I've seen estimates of 5,000 people in the US. What this means is that people arguing against a wealth tax are happy to disadvantage 330m people to protect the wealth of a low number of thousands.