I think they know what they're saying, come on the first thing anyone learns of any foreign language is the swearing
but since it's cuss words in another language it doesn't really mean much to them so they say it
for example I use "damn it" in english more often than not, but it's really hard for me to say "maldita sea" (spanish) cause it feels like it's a lot worse, yet both have the same meaning.
As devilayu said, asian countries tend to censore more anything that's sex-related than regular swearings, I was reading in a website two weeks ago that the premiere of Desperate Housewives in an asian country had to be edited and reestructured to delete the sex-related scenes/conversations.