I think that dual languages are not a safety hazard. On the reverse, a flight crew can become too complacent if ATC is only conducted in English.
This is a new one. Complacency. Are you suggesting that a bi-lingual frequency "keeps everybody on their toes"? Procedures and standardisations are implemented to ensure saftey is at it utmost. In a BUSY terminal or ground environment, with more than one language being used, how can any pilot honestly say situational awareness can be kept?
You mention the ONLY incident that comes to you attention was that unfortunate one at CDG. This is gonna sound a little sensationalist, but will it take more deaths to seriously address this issue?