President Obama worked successfully to end discrimination against gays in the military and moved swiftly to implement a Supreme Court ruling protecting married gay couples from federal discrimination. But gay rights advocates are upset about something he has not done that they say he could accomplish with a pen stroke: an executive order banning federal contractors from discrimination based on sexual orientation or gender identity. Advocates say an order would provide employment protections for about 11 million workers who currently have none. Many of the nation's largest companies and 21 states, including California, already have policies or laws against sexual-orientation...