This is interesting because I find it counterintuitive. I would have thought that the tendency would be the opposite: that, for a given thought, expressing that thought in German (your native language) would tend to make it more sympathetic to you rather than less (all else being equal).
Data such as this may force me to reevaluate my predictions of the effect one might have on an audience by speaking to them in their native language.
The effect in question is actually attenuation through mediation: most people can attest to the fact that foreign swear words are not perceived as strongly as the native ones, even if the meaning and usage is identical. Having an intermediate step of translation reduces emotional impact. Not surprisingly, the effect wears off after living long enough in the new environment. This has little to do with framing.
Interesting new paper (anyone have a link to an ungated version). Abstract (emphasis added):