It's the other way around: you're less emotionally connected to your second language. You're not phased by the most scurrilous elements of English, because of a combination of factors (like the way your brain processes a second language, and the fact that you did not grow up in a native English culture). Whereas you have a primary connection to Dutch and its native culture, so you instinctively know what is vulgar or disgusting in a much more direct way.