Equal pay isn't a partisan issue. Is it?

The outcome of the Ledbetter Fair Pay Act (see post below) yesterday: killed. By filibuster. From AHN:

Republicans in the Senate successfully prevented Democratic colleagues on Wednesday from considering a bill that would have overturned a Supreme Court decision giving employees only 180 days to make pay discrimination complaints. The filibuster by Republicans stood with a vote of 56-42, or four votes shy of the required 60 that would have overcome the legislative obstruction and allowed lawmakers to take up the Lilly Ledbetter Fair Pay Act.

Its proponents are baffled:

"I don't know how anyone would oppose something like this. It just makes sense that people should be treated fairly," Senate Majority Leader Harry Reid (D-NV) said in a statement posted on his website.

Senate Democrats blame Republicans for blocking the vote to protect employers from litigious workers. But what about protecting workers from employers who seek to pay them differently based on gender, race or religion? Can somebody clarify this for me?