Almost everything being done right now is anti free market, so what would it matter to libertarians if some rules are repealed and some others are enforced?

The major issue that there is, is that goods are imported from countries with far less regulation, some from abusive countries, and then sold in the local market at a premium, satisfying investors and stealing jobs.

Tarrifs could be used to leverage manufacturing jobs back to the community for a while, however that would involve a lot of responsibility in managing foreign affairs, primarily by avoiding to start new conflicts and securing trade routes. This would depend on having a system based on sound money and not one which exploits inflationary practices, so that manufacturing can actually get its engine revving to create a system of stable production and prices for goods and services.

If china tries to lower production prices by abusing its workers or shirking responsibility on regulated production, then they get punished for it through tarrifs. It's really not an ideal situation to be in, however you need to keep in mind that your $1500 iPhone is made in a factory which has nets outside to catch people trying to kill themselves. I think people should be discouraged from purchasing such products that generate little to no taxes to the local community.

So while I as a libertarian am against tarrifs, I wholly support anything that puts local manufacturers on a level playing field.