This is one of those episodes that really defines the characters. Jerry and Elaine meet up with a married couple they've been "waiting out" -- Jerry wanting to date the woman (Debra Messing) and Elaine pining for the man (Cary Elwes). After George makes his usual thoughtless remark and accidentally splits up the couple, Jerry and Elaine jump onto them like vultures onto a rotting carcass.
The characters on "Seinfeld" are famously amoral, and this is a perfect example of that -- the precipitating incident is caused by one of them not thinking and the rest of the episode is driven by two others simply not caring about anyone other than themselves. Only George shows any conscience here, trying to fix his original error (and even that isn't so much because it's the right thing to do but because he feels guilty).
I still can't figure out why the characters on this show, all of whom would be so completely unlikeable in real life, have become cultural icons. But darn it, there you are.