6:30 PM PT -- We got video of Amy while she was being detained, and she got a police escort ... to take a pee. She also says she's remaining hopeful about stopping Kavanaugh's confirmation, and isn't going to stop the fight.

Amy Schumer talks the talk and walks the walk when it comes to denouncing Brett Kavanaugh -- 'cause she just got arrested in D.C. with a bunch of other people protesting the imminent vote on his confirmation.

Amy and other protesters were shepherded by D.C. police Thursday inside the Senate office building on Capitol Hill, where an officer asked if she wanted to be arrested. Amy didn't hesitate ... she said yes while holding a "We Believe Anita Hill" sign.

She also had a green shirt on that seemed like it might be a play on Melania Trump's tone-deaf "I Really Don't Care" jacket.

Amy was later seen in a lineup against a wall, where she and others, including Emily Ratajkowski, were being detained. We don't know yet what she's been arrested for ... possibly disturbing the peace or trespassing.

The mass protests in D.C. are in reaction to the FBI concluding its investigation, launched after Dr. Christine Blasey Ford testified last week about her sexual misconduct allegation against Kavanaugh.

It appears what the FBI came back with hasn't swayed the vote of key Senators -- which means Kavanaugh is likely to be confirmed to the Supreme Court.