That is a good point, and of course the episode is written by Americans. But Spike clearly means it in the secondary meaning (which comes up as the primary meaning these days when I check both Oxford and urbandictionary, but that may not matter). Furthermore, the Swedish word for pimp only means "someone who profits off prostitutes" - it has no connotation whatsoever to femininity, flamboyance or supposed unmanliness. So even if the original's translation from US English to UK English is shaky, the Swedish translation may be technically correct based on the actual line, but obviously incorrect based on what's actually on screen.

Also, the same episode has the line
Buffy (...) had her lesbian witch make with the beaucoup de magie
translated as
Buffy fulfilled her lesbian wish with lots of magic
which I believe didn't happen until the *spit* comics. ;)