I think it's a fair trade if you want to continue to run a business in a country, that country has a right to summon you to explain what your business is doing.
The right to summon the local corporate representative, legal team, etc.? Sure.
Does every country have the "right" to summon a multinational CEO? That'd get crazy really quick, and I doubt it'd benefit anybody (beyond politicians.)
I had the same reaction as the parent comment - to "request" his presence is perfectly fine, but a "summons" would be a bit much...
It is a request. There's no sanction associated with not turning up, but that means Facebook doesn't get a say in what the legislative response to this is. For example, maybe a ban on political advertising on Facebook.
Not as of now. Though until very recently, you also needed to have at least some personnel physically present in a location if you wanted to conduct business there.
As that changed, thanks to the internet, those rules might need to change as well.