It used to be that tariffs were one of the most significant ways for the government to receive revenue, but that has changed in the modern era, in which tariffs have typically been eliminated or reduced considerably in favor of "free trade." However, just because tariffs have fallen out of favor doesn't mean that a particular administration can't bring them back for various reasons, good or bad.
When it comes to international trade and business, so of, all the players need to agree to the terms of that trade, and know that the rules of the road are not subject to change due to arbitrary decisions which have not been properly reasoned out, and previously debated upon and discussed, with each party having the opportunity to have their say. In other words, tariffs implemented that appear to be done as a form of "punishment" or a way to exert pressure on countries that do not have the resources and overall strength that the United States represents are not just going to be resented by those suffering from the new tariff structure but are going to be seen as being unfair and unreasonable, which is why they are bad for international trade and a poor way to deal with countries when it comes to trade. That said, the least America should do when it insists on implementing tariffs is to do so in a way that doesn't hurt our domestic poor and disadvantaged, meaning tariffs should be segregated into categories, basically necessities and luxuries. That is to say, things that everyday families must expend their money such as on food, clothing and general goods should not have to suffer from tariffs; whereas luxury goods such as hi-end vehicles, and non-necessity items that are considered to be status symbols or of prestige should be subject to a higher tariff.
When it comes to tariffs being indiscriminately enforced, there needs to be a recognition that higher prices on goods that consumers must have are going to mean more money coming out of their pocket, and in the absence of a higher income, this is going to squeeze those consumers more. So too, higher tariffs are quite frankly going to lead to higher inflation, and thereby less purchasing power. Again, that doesn't mean that tariffs are necessarily bad; it just means that they should be carefully considered, because tariffs affect the bottom line of money expended and thereby not saved, and because there is a significant swath of Americans who struggle paycheck to paycheck, this signifies that the worst tariffs are those that impact negatively the most vulnerable amongst us.
In sum, trade is important to countries, and obviously countries want that trade to be beneficial for their nation, and typically such trade is beneficial from the buying end when the items being purchased from foreign lands are cheaper than what they would cost if manufactured domestically, which is why imposing a given tariff needs to be carefully considered because imposing that cost upon the consumer is a form of taxation, which should not be regressive, but rather should be progressive in its tax effect.