Is Ignorance Bliss?

So, I recently saw a poll on deviantart. It asked whether you'd be stupid and happy, or smart and unhappy. Surprisingly, to me at least, the significant majority of the people who answered said they'd rather be stupid and happy.
I said I'd rather be smart and unhappy, because then I would know about all the problems and I could fix them.
This is coming from an environmental science major. That being said, this major can be incredibly depressing at times. But not always. The whole point is not to watch the world die. It's to save the world.
But the depressing-ness is why a lot of people don't want to learn anything about it. They choose to remain blissfully ignorant. This is one of the reasons some people vote for a guy who assures them that everything is all right. They don't want to vote for someone who says that the world is gonna fall apart if we keep doing everything that we're doing. People like their wasteful lifestyle.
But if everyone remains ignorant, nothing will ever change. The world will sit in the same place indefinitely. People need to learn and change.
For example, if someone's gonna come and whack you in the head, would you rather sit there unaware until you get smacked, or would you rather know the guy's coming so you can stop from getting hit in the first place?
Also, a good point someone made on the poll which I'd though about before is this: How can you be happy if you don't have anything unhappy to compare it too? You can't be really happy unless you've known unhappiness. Otherwise everything it monotonous and exactly the same.
And then several people also said "what if you're too stupid to know that you're happy?"