You must have culture to defend yourself against enemy tourism, but not tourism itself.
This is one of the most oft-repeated bits of misinformation since BNW's launch. It's wrong, and is a path straight to piles of unhappiness.
Tourism serves as defense against enemy tourism, because unhappiness is generated based on the DIFFERENCE in influence between your civ and another civ. If you have no tourism or very minimal tourism, you will be crushed with unhappiness from other ideologies, even if you have a fair bit of culture. This is because if your influence with another civ is "Unknown" (level 0), the other civ's influence with you only has to be "Exotic" (level 1) before the ideology difference starts generating unhappiness. Even civs with fairly modest tourism are likely to be Exotic over you at some point in time, and if you're not Exotic over them back (and your ideologies differ), you start picking up unhappiness. If you manage to at least maintain parity, you're free and clear. Similarly, if there's a tourism juggernaut who's several levels of Tourism influential over your civ, they're going to be generating a lot of unhappiness in your civ, but they'll be generating a lot more unhappiness if you're not even Exotic with them.
The unhappiness penalty from ideology difference is based on the number of cities you have or a fraction the population in your cities. If you have a large puppet empire, it'll be huge, and you should do everything you can to protect yourself from it. (Crushing tourism-focused civs first is important too.)
Culture is important for defending yourself from enemy tourism, but unless none of them ever generate much tourism at all, some of them are going to be Exotic over you eventually, regardless. You want to be Exotic back.
