I've noticed something similar as well. For a few years now, I've favored calling something "silly." In context, it's connotations are just as bad - if not worse - than harsher alternatives, but it doesn't trigger people's curse word sensor.

On the other hand, using harsh words rarely has power. If someone you've never heard curse before calls something "bullshit," you'll take notice. This only works, though, if you swear so rarely that people take note that when you do, it has meaning.

In other words, swearing casually removes the power of swearing.