We already know where this is going.

For some of us, the knowledge is hateful, for others, hopeful. Yet the inevitable arc of it is clear: Maybe it will be 10 years, maybe 20, but we can now envision a day when the last legal restrictions against gay men and lesbians will be struck away.

A future is coming in which they will be fully protected from discrimination in housing and employment, free to fall in love and tell it to the judge, to make end-of-life decisions for their partners, to adopt children. And we will look back, vaguely amazed, that such things were ever in controversy, that there was ever a time sexual orientation was used to deny basic rights and privileges.

The latest giant step in that direction was taken last week in a hearing of the Senate Armed Services Committee. There, Defense Secretary Robert Gates and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, testified in favor of ending the Pentagon’s stricture against gay men and lesbians in the military and of striking down the 17-year-old “don’t ask, don’t tell” law under which they are required to hide their sexual orientation in order to serve.

The Pentagon has ordered a review of the potential impact of repealing the law. “Speaking for myself and myself only,” said Adm. Mullen, “it is my personal belief that allowing gays and lesbians to serve openly would be the right thing to do. No matter how I look at this issue, I cannot escape being troubled by the fact that we have in place a policy which forces young men and women to lie about who they are in order to defend their fellow citizens.”

And if some of us found that a bracing statement of a self-evident principle, others were unconvinced.

Indeed, Republican Sen. John McCain, more politically agile now that he has jettisoned the weight of integrity, promptly reversed a 4-year-old promise that he would be guided in this matter by the opinion of military leaders, instead pronouncing himself “deeply disappointed” by Mullen and Gates’ testimony.

There is always someone who fights a rear-guard action against progress, and if he is still around to see how his words play in the history books 20 years from now, it will be entertaining to hear how McCain explains himself.

That said, one’s satisfaction in knowing the military is poised to end its sexual segregation must balance against the frustration of how long it took to get here. After all, the basic architecture of this issue has not changed since 1993.

Gay people haven’t changed. Service hasn’t changed. No, what has changed is us. We watched “Will & Grace,” we made gay friends, we found some measure of the acceptance that had always eluded us.

There is a temptation to say this is just the way progress moves, that time must be allowed to do its work. We do the right thing — eventually.

It is seductive, this idea that you and I have the right to put a timetable on other people’s freedom, that they deserve it when we are ready for them to have it and that until then, they should simply endure, simply be patient.

But if it is wrong now to deny a man the right to serve because he is gay, that means it was wrong then. If it is a foolish waste of resources now to kick a woman out because she is a lesbian, that means it was a foolish waste then. If “don’t ask, don’t tell” is a cowardly compromise with hysteria and homophobia now, then it always was.

So one’s satisfaction in this inevitable march of progress is tempered by a recognition of how many careers and futures were needlessly broken along the way. We know where this is going, but that doesn’t mitigate vexation at the fact that we could have been there long ago but for stupid intransigence and fear.

Patience is such an easy word to say.

— Leonard Pitts Jr., winner of the 2004 Pulitzer Prize for commentary, is a columnist for the Miami Herald. He chats with readers from noon to 1 p.m. CST each Wednesday on MiamiHerald.com. lpitts@miamiherald.com