What grinds my gears...
Then I discovered that this quote was not actually by Voltaire, but a bastardised misquote of "To determine the true rulers of any society, all you must do is ask yourself this question: Who is it that I am not permitted to criticize?"
Whew, that's a mouthful. I can see why it was shortened.
It also originated not with the venerable Voltaire, but a man called Kevin Alfred Strom, who is undistinguished apart from being a neo-Nazi who was imprisoned for possession of child pornography. Nice piece of work, isn't he? Definitely the guy you want to be taking advice from.
A number of you will be pointing out that - as detestable as Strom is - his repulsive actions don't necessarily make his statement logically wrong. I happen to agree with this.
His statement is still bad and wrong anyway.
If you consider yourself a brave freedom fighter, valiantly standing your ground on the perilous battlefield that is social media, you may have posted this quote. You probably think it's right.
If you live under an authoritarian regime where criticism of the ruling class earns you the ire of the state, you probably are right - although in that case, the displays of state power are so blatant that edgy neo-Nazi misquotes are unlikely to be of much use to you.
If you live in a reasonably liberal Western democracy, where speech is usually much more free (apart from hate speech - I don't want to go into this now), things are a little different.
One of my pet peeves is that people will go on and on about freedom of speech and not realise that it doesn't include freedom from criticism. That is to say, you can say something which will offend someone, but the offended party can and probably will retort. If you can't deal with it, that's your problem, quite frankly. That doesn't mean you're not allowed to criticise them - it means that if you do criticise them, they have every right to respond and are under no obligation to even do so nicely.
This is what a lot of people sharing this quote don't understand: someone disagreeing with you on the internet is in no way the same as potentially being imprisoned.
The context in which this quote is used is also bad and wrong. Because it implies that disagreement is equivalent to censorship, it's incredibly insidious: anyone who dares to openly criticise you is acting as part of a conspiracy to silence you. As such, you could theoretically use it against feminists, leftists, Muslims, PoC, disability rights activists or especially Jews. The latter is what's mostly done in practice. Considering that Strom is an anti-Semite, this is somewhat poetic.
If you're truly interested in freedom of speech, this post is not the be-all and end-all. There's lots I've missed out. But equating criticism in a reasonably liberal democracy with displays of state power is extremely dishonest and usually acts to silence people who have been historically silenced anyway.
Just because people you don't like were mean to you on twitter once doesn't mean they're all in on a conspiracy to control the world. Grow up, learn to take situations apart critically, and don't cry and post dank edgelord memes when someone disagrees with you.