What differences between older and newer unions tended to cause tension within the labor movement?

The difference is that the older union tend to pursue practical things such as fair wages, number of holidays, and working hours.
The newer union on the other hand, tend to focus on something that related to social justice, such as fair treatment between each races, same opportunity to rise the ladder, etc.

Sir thomas more, venerated in the catholic church as saint thomas more, was an english lawyer, social philosopher, author, statesman, and noted renaissance humanist. he was also a councillor to henry viii, and lord high chancellor of england from october 1529 to 16 may 1532. i found this information on wikipedia