In Star Wars, why is the bartender at the Mos Isley spaceport cantina so hostile ("we don't serve their kind here") towards C3PO and R2-D2?

Probably just to show that even a long time ago in a galaxy far far away, racism still exists.

Probably because droids are a well sought after commodity.The motley collection of patrons that frequent that dubious establishment would more than likely do damage to the premises in their attempts to illegally acquire one.

Since droids do not drink,, they would just be taking up space !

For the same reason why he probably wouldn’t serve a mushroom or a piece of string (or rope).

@mrentropy

“Hey, aren’t you that rope I kicked out of here a minute ago?”
“No, sir, I’m a frayed knot”

Because droids are whiny in the Star Wars universe?

@JeanPaulSartre if that was the reason, the bartender should have kicked Luke out before he got anywhere near the bar!

@MrItty lol. Honestly surprised he didn’t smack him for tugging on his sleeve.

@Pretty_Lilly Not true. Any bartender could have made a killing off of Bender

He was dangerous when sober.

Droidism.
Tattooine, backwoods planet that it is, hadn’t previously adopted some of the more progressive policies of the Republic and oppressive rule by the Empire definitely didn’t do anything positive for Humanoid/Droid relations.

Since the Empire’s fall, R2D2 had pioneered great advances in the Robo-Civil rights movement. Sadly, during the annual Skywalker day celebration, the influential droid was robonapped, deactivated, disassembled and sold for scrap by a radical Jawa fanatic but R2D2’s committment to the cause has not been forgotten.

The Mos Eisley Cantina is a crowded place with very few women. When a woman comes in, the establishment would prefer she intermingle with the other guests, and not be distracted by the presence of droids which many of she would ultimately end up using to text-message her friends and read emails all night long, instead of mingling or buying beverages.

It is rumored that Morgan Freeman has been slated for the role of R2D2 in an upcoming bio-pic.

OKAY. Now that nobody given the real answer…
In the extended universe, it’s explained that the owner of the cantina, Chalmun, doesn’t like the droids because they don’t drink… so they take up valuable space in his bar. He’s the one who had the droid detector put in.

The bartender, Wuher lashes out at the droids because they are the only creatures who won’t try and fight back. He hates everyone, so they are just an easy target.

I have NO idea what you guys are talking about up there… but nice try.

He knew better than we do now that the computers eventually rise up and attack their masters.

It has become a legend in the galaxy, that all droids have a little bit of R2D2 in them.

they weren’t the droids the bartender was looking for?

Maybe Bender (Futurama) had been to the bar previously and if these robots are anything like Bender the bartender didn’t want them around drinking.