There is truth in both sides of the arguments; tarrifs can be devastating to your industry if you do not produce the necessary inputs in your sphere or own nation, but can be useful to cover the costs of lots of clergy or crats if you are trying to pump up literacy or improve crat efficiency.
I would like to add a few thoughts about tarrifs that I've had. First, tarrifs can help keep cash within your nation and not flowing to other nations. Every pound or dollar that leaves my country via imports means that my pops are essentially helping other nations by buying their goods and driving that country's industry, which may not be in my best interest with certain products; I understand that this cannot be avoided completely, but the idea is to strike a good balance with the goal of securing such necessary resources for my own nation.
Ish. Problem is, good are bought hierarchically - so if your POPs are spending 5% more on importing grain or fish for their life needs, they have less money to spend buying your locally-produced manufactures for their everyday needs - so you're cutting down your home market for the goods factories are selling at exactly the time that you're increasing the cost of making them. Again, this isn't so bad for uncivs; they have no factories (or '2 or less', anyway), and tend to rely on RGO income and laughable TE. But it still hurts the Artisans to an extreme level, which can painfully impact on the largest source of potential Capitalists you have available when you hit the civ button.
Tariffs can be used successfully, but it's kind of an advanced tactic and is painfully specific in the circumstances that it's a good move. Every other source of revenue is better, since they don't impact on production - and the time you're most likely to need to use tariffs for revenue purposes is in the early game, when you don't have many clerks or efficiency techs, so they cause the most damage to your industry (and so your long-term growth, and place in the buying order). Basically, it boils down to 'use them if you must, but tariffs hurt you a lot more than basic taxation will'.
I actually tend to cut spending rather than raise tariffs, tbh; since the slider POPs all compete with one another, if I particularly want one type (say, crats, to cut my outgoings), then I'll spend 100% on admin, cut clergy to 50% and military to whatever else I can afford. My crats will increase faster for it, I'm saving money, and all I'm really losing out on is a couple of 0.0001% lit gain. It only takes a few years of that to get to full admin, when I can drop admin spending to 50% and turn up the clergy.
That said, I
have played in MP games where co-ordinated tariffs have been used to decimate opponents, however. Having Russia, the UK and Austria or France all suddenly raise a big tariff can shatter industries in other powers in the early game; it also tends to retard industry globally by quite a bit, including your own. You can effectively bankrupt some opponents, but only if you're collaborating with 2-3 of the biggest, nastiest GPs around already and are also willing to trade some of your own future prosperity just to be a dick to countries half your size - and really, if you wanted to screw the game up for them that much, and had 50% of the armed forces of the world on your side already, there's better ways to do it.
Second, I would like to point out that you can effectively make certain goods exempt from your tarrifs by setting up a buy order and checking the box that allows pops to buy from your stockpile; coal, cement, and other essential factory goods are excellent examples of what I'm referring to.
Don't use that button. Like, ever. Are we having this conversation from 2010 again?
Buy from stockpile causes all kinds of money funkiness - for example, starting with a stockpile of 0, turn it on and put grain to +2000. You POPs will be demanding the exact same amount of goods from the WM - but buying it from the stockpile - which will then also demand 2000 grain to replace it. You've just manufactured 2000 demand from nowhere, but you're not adding 2000 supply - only you can buy that grain, so it's not added into the value calculation. d=!d and price insanity follow.
Incidently, this can be great fun to watch if you just pick 5-6 primary goods, stockpile 2k, and then set 'buy from stockpile'. Or that might just say something about my idea of what makes for a good Saturday night.