"The Drumhead". They play TNG most days on Channel 11 in Aus. I only get to see the Saturday airing though (my wife gets to see it every day!)
The Drumhead is one of those episodes that gets better every time you see it. Shockingly prescient, really. Absolutely laced with great lines:
'With the first link, the chain is forged. The first speech censured...the first thought forbidden...the first freedom denied--chains us all irrevocably.'
"We think we've come so far. Torture of heretics, burning of witches, it's all ancient history. And then, before you can blink an eye, suddenly it threatens to start all over again. But she or someone like her will always be with us, waiting for the right climate in which to flourish--spreading fear in the name of righteousness. Vigilance, Mr. Worf. That is the price we have to continually pay."
"THAT IS NOT A CRIME, WORF!"
"Have we become so fearful? Have we become so cowardly that we must extinguish a man because he carries the blood of a current enemy?"
Also I loved them accusing Picard of breaking the Prime Directive nine times- hilarious wink to the fans!