Offensive speech can now be suppressed through trademark law.
Uncomfortable truths were always allowed "to see the light of day" before the case (except by liberals on campuses). The KKK can call themselves the KKK; they don't need a trademark to do that. The plaintiff was allowed to call themselves "The Slants" or use "Slants" on t-shirts, etc. The uncomfortable truth was seeing the light of day, as you say. But, the band wanted to stop other people from using that word for those purposes, so they filed for a trademark.
The issue before the court was whether one person could have a government endorsed monopoly on an "uncomfortable truth" in order to market a product or service.
After this decision, if you start using the word "slants" in the field of stage performances or music, the band can sue you to stop you. If you use the word to market t-shirts, you can also be sued. That's why the link to the professor I quoted is "Only I can disparage you!"...if anyone else uses that disparagement, they may be sued, and the government (through civil enforcement) will shut them down. This is an anti-free speech decision, to my mind.