[Alneyan]

Not quite: 50 happiness will only increase your trouble getting your guys and gals happy, but it will not lower your happiness, so you will not get insta rioting. Neutral races have that one advantage: they are slightly less likely to be unhappy than the others. Even a Peaceful race needs less than 45 happiness, if memory serves, to start having happiness going down to Unhappy and below while nothing happens.

Oh, and be careful when signing agreements: in a game where I took over a neutral, I got several alliances on a single turn, and almost killed my Empire because of that... They all rioted since they obviously didn't want any alliance. *Sighs*