The Court has now said that not only do you have a right to free speech, but you now have a right to have the government quiet the crowd down for you.
The Court mixes, once again, issues of rights (restrictions on government power, like free speech) and government provided benefits & powers (positive uses of government power, like trademarks, to stop free speech). [The reason I think this is a turning point is that although the (usually liberal) justices have toyed with treating the use of government power as a right, I'm not sure they have been unanimous in doing so.]
Rights: Before the decision, the band in question could always call themselves the Slants if they want to do so. The issue before the Court was not whether they could call themselves that name, and put that word on their posters and t-shirts. That was a given, and not disputed.
Government Power: The issue before the Court was actually whether the band could use the power of government (through trademark law) to prevent other people from using the word "Slants" on their t-shirts., etc. That is not a classic free speech issue. It's kind of the opposite: when can speech be restricted? The answer, according to the court, is that speech can be restricted (on constitutional free speech grounds, no less) in all trademark uses, whether those uses are disparaging or not. Not only that, but the Constitution requires this restriction of free speech...which is the most incredible part of the case.
I'm not saying I dislike the outcome. You can argue that the law should not have been passed. I just think the Court is misusing the Constitution, creating a "right" not only where there is no such historical right enumerated or traditionally understood, but also where it is totally inappropriate to create such a right.
I think it comes down to the fact that the Court didn't want the Congress to pick trademark winners and trademark losers. I get that. And, I see potential for abuses of that. But, I just don't see how that is a Constitutional issue. The answer for that is to elect a new Congress. But, if the past 8 years have proven anything to me, it is that the Constitution is now whatever we say it is.