If one could specify an answer to this question, it would be constructive to make some observations and a reader could make their own conclusions. I recently read that this sort of exercise is an example of "choice architecture" where the points presented predispose specific conclusions. So in an effort to be explicit, I think the answer is disunity.
The first observation is the ALCU
which many consider to be the premier civil rights organization in the US. When one looks at the the policy list in the article, it should be noted that worker's rights are absent. One may reasonably argue that freedom of speech is an important aspect of worker's rights but one can also that freedom of speech doesn't really apply in a work place.
The next issue is a bit harder to document but not so hard that some digging will support my point. Labor Unions in the US have a history of opposition to inclusive civil rights. It has been argued that blacks have been historically recruited in the south to break strikes in what is now called the rust belt. The major Unions have only recently embraced immigrant Hispanics as prospective members. Some of the fastest growing unions today are made up of Hispanics service workers, mainly in janitorial work.
Police Unions are common in the US but given, the police are responsible for public order, they have been used in ways to suppress unions. The relationship between the police and minority communities can not in general be said to be good. The police, having a responsibility for public order have often been at odds with civil rights. Strikes do cause disorder and strikes are the primary instruments of unions to cause change.
Teachers Unions are strong in the US and they in general support civil rights, but are viewed as being part of the problem in education in the US.
A historical disconnect between civil rights and the new economy.
Many Tech workers, particularly those in the Baby Boom generation will cite the Moon landings as a motivation to pursue a STEM education, while Rev Abernathy categorized the Space program as immoral. It might be noted that outside of academia, there is only one significant union of engineers in the US at Boeing.
STEM related professional societies exist to promote their profession and typically think of themselves as international institutions, so issues like H1B tech visas involve choosing one sub group over another. While Unions have adapted to some aspects of the new service economy that success hasn't included the majority of knowledge workers.
while some might say that professional organizations are unions by another name, workers rights are peripheral and sometimes at odds with workers rights.
Fundamentally, there is no common solidarity with a common ideology centered on workers rights. Unions are perceived and largely act as a special interest. What many call "progressive" only partially includes organized labor. The connection to Civil Rights is not strong.