It is not boneheaded to express your constitutional rights.
It is boneheaded to protest using hate and disrespect. That is what CK is doing and that is why we should ALL see this as a wrong method of protest. Wearing socks that have a prejudice statement on them is hateful. And it is EXACTLY what CK is protesting. That is boneheaded. What if his socks said Women are Pigs? Blacks are Pigs? Jazzfanz are pigs? Is that ok? Is that a protest? All cops are not pigs. Some cops are racist. Some women are racist. Some whites are racist. Some _______ are racist. The very farthest extension of this hate protest is the sniper killing of cops.
Also, while not as clear cut, it is wrong that he is disrespecting the USA and all the persons who have fought, died, volunteered for having a free country and the right to protest. He is disrespecting those who volunteer at schools, coached little league, do city council, etc, etc to make our country great. Racism in this country and any other form of hate is not espoused, codified, or in any manner formally institutionalized by the USA. Women run for president, Blacks make 10s Million a year in their chosen profession, etc. That is not to say there is unjust behavior by individuals, or formalized institutions like a police force. It is possible a whole police agency is racist, due to corruption. But the police/law enforcement as a rule across the USA is not a 'racist org'. So his efforts, in my opinion, are not only wrong but are adding to the racial divide. Many of you reading this are preparing to write about the injustices of the minority communities which constitutes 'institutionalized racism'. That's real. That's debatable as to the extent/manner, but it is not codified "women can't hold office" or "blacks count as 2/3 of a citizen." Stuff like that.
So - he is boneheaded for using hate and disrespect as his method to 'protest'. If, for example, he organized a rally in downtown SF and wore shirts and socks and held signs that were NOT labeled with hate, but rather a plea for justice, and did so as a law abiding citizen, I would give him two thumbs up. If I lived there, I might join him. But even moreso, if he were to use his fame and money for a community outreach program with cops and citizens, I would become a 49fan. (That's saying a lot.)