Tariffs are very bad. Trade brings wealth is a very good saying and without trade you can't have wealth. The economy as a whole can be most productive and have the cheapest prices when there is free trade and tariffs are not prohibiting the economy. An example in the video was the avocados from Mexico. This is talking about how much cheaper it would be to produce the avocados in Mexico than in the US.
Both political parties like tariffs because it makes them seem like a good American. The idea is that tariffs support American jobs and supporting American jobs is supporting Americans which makes you a true patriot. Most Americans are more likely to vote for a candidate who wants American success or at the very least claims they want it. So most politicians use tariffs as a way to get more votes for themselves.