Reactions to this vary.
I always tell people not to swear in a foreign language until they are fluent in that language. The problem is that it seems like a fun game to you. You're saying a cute, little naughty word that doesn't carry any baggage. For you. To the other person, you probably just said something offensive or, at least, wildly inappropriate.
Imagine that the situation were reversed. You're walking down a street in Italy, someone recognizes that you are an English speaker, walks up to you and says the following:
Mi dispiace, non parlo l'inglese ma F!@# you.
What part of that is going to resonate viscerally? Now you know what it sounds like to them.
Further, each culture assigns a different weight to swear words. In some cultures, one would never swear in a public setting. In others, swearing might be considered a very mild issue.
Each word (or phrase) also carries an individual weight. So just make sure that you know the potential impact of what you are saying before you say it.