Obi-Wan Kenobi: "Mos Eisley Spaceport. You will never find a more wretched hive of scum and villainy. We must be cautious."
Obi-Wan has been all over the galaxy and seen many more wretched hives of scum and villainy. He's been to Geonosis, which was where Count Dooku was building a droid army. Obi-Wan has been in the Chancellor's office, and that surely counts as a hive of villainy. And don't get me started on the Galactic Senate! Then there's the hive of villains at Utapau and Mustafar.
And we know Luke ended up in this wretched hive of scum and villainy.
What was so bad about Mos Eisley Spaceport?
It can't be the fact that their bartenders discriminate against droids.