If it was a sudden reveal I suspect you'd be correct - though that time of chaos could be an interesting setting. Is a "big reveal" the only option? For that matter, you make a case for those in power being aware of it since the Inquisition...wouldn't that lessen the impact of a public reveal?
I don't watch much Star Gate, but I did see the start of one episode when the newly elected president is being told The Secret. His initial reaction was "Good one, you had me going there for a minute", followed by "Wait, the Earth's been invaded I didn't know about it?".
In theory, we could have a star gate and only the people at the top know about it. In theory, in the DV, the president and the "Gang of Eight" might know all about magic. There could be small scale SI type groups working for every nation's government - a bit like White Wolf's Vampire the Masquerade game where you had "Project Twilight" handling X File stuff. Small, elite teams that know magic is out there and doing what they can, answering only to the top level of the government.
But that's not magic being public.
No, magic being made public means we all hear about it. When the secret becomes common knowledge - and there's got to be a big reveal to have that happen. Even if 100,000 people in the DV version of the USA know and accept that magic real, hundreds of millions don't. There's paranet, there are those weirdos who join the DV version T:. T:. and other "magic groups", then there's the average man who has never encountered magic. The big reveal is for the last group.
How would they react? I'm not sure, but probably with fear and maybe with hatred. All it takes is one "They're of the DEVIL" preacher on the radio and people will wonder if they are safe from wizards.
Think of it this way:
A wizard could walk up to the POTUS and cast a lightening bolt to kill him. There is no way to detect if the person is a wizard and no way to disarm him - and there might be a wizard who's also a terrorist, so the POTUS isn't safe. If the POTUS isn't safe, then how am I safe? How do I protect my family?
A wizard could read my mind and learn all my dirtiest secrets.
A wizard could cast a spell on me and make me do terrible things.
Ah, you say, there are laws of magic against that.
But who makes the laws? Wizards.
Who detects when the laws are broken? Wizards.
Who enforces the laws? Wizards.
So I'm supposed to believe that wizards will keep me safe from wizards? Really?
Then there's the fact that terrible things happen to nice people. When there's a strong belief in magic there's usually scapegoating. Here's the "logic" behind it:
Your crops failed? Obviously someone cast a spell on them to make them fail. Is it that weirdo? Maybe if we kill that weirdo we'll be safe.
Could a wizard make your crops fail? Probably. Can that guy prove that he didn't? No. Can he even prove that he's not a wizard? Of course not.
Take away the paranoia and it still doesn't look good for wizards:
Reporter: "So there are real vampires out there? Do wizards protect us from them?"
Wizard: "No, we signed the Accords so we don't fight them except in certain circumstance."
Reporter: "Oh, but there are these things from another world called fairies that prey on people. Do wizards protect us from them?"
Wizard: "No, we signed the Accords so we don't fight them except in certain circumstance."
Reporter: "Oh, but there are Fallen Angels riding in coins and preying on people. Do wizards protect us from them?"
Wizard: "No, we signed the Accords so we don't fight them except in certain circumstance."
Reporters: "So you don't protect us from any supernatural threat - WTF good are you? Hey, my cousin disappeared three years ago - did something eat him? Did something you made a deal with eat my cousin?"
Or even the laws of magic:
Reporter (in a different interview): "Your group enforces these seven laws of magic, is that right?"
Wizard: "Yes."
Reporter; "And in most cases, your group is the only ones who can detect if those laws have been broken, is that right?"
Wizard: "Yes."
many questions later
Reporter: "So you're saying that there are seven laws of magic, which your group came up with. Yours is the only group that knows if someone is breaking them. You have a paramilitary wing that arrests people for breaking these laws of magic. That group is authorised to use lethal force when 'arresting' suspects. If they survive an arrest, your group gives them a trial where they are not allowed lawyers, fifth amendment rights, and the trials almost always end with an execution. You do this even though you have no backing from any state, federal, or international authority. Have I got that right?"
Wizard: "More or less."
Reporter: "Then may I ask how many US Citizens you have murdered this way?"
And the wizards are the nicest supernaturals out there.
If I lived in the DV during the big reveal, I wouldn't want to work the night shift - because if I only came out at night then people might thing I was a vampire. No, I'd make a point to be out in the daylight. And I might even carry an iron nail to poke myself with to prove that I'm not a fairy. And that I bleed red blood. Because there would be scared people who would want to see that proof and I don't want a mob to lynch me. And they might do that anyway, because they are frightened by what they don't understand.
But give it a year or two and things will calm down. Humanity can get used to anything. History has shown that when we get hit with real fear - from the fear of WWIII to terrorist bombs - we slowly slowly adapt to the new normal and get on with life.
Richard