There are certain gambits that you probably shouldn't try against a strong Grandmaster.  I'd put the Budapest gambit in that category, and certainly the Smith-Morra gambit in the Sicilian.  Here we have a 2300 player trying the Blackmar-Diemer gambit against Dmitry Gurevich. This game occurred at the Illinois Open in 1993.

While I can't call this game a refutation of the Blackmar-Diemer, it certainly is quite enough to send White back to the drawing board. If you study this game, you will gain understanding of a good way to handle this semi-sound Pawn offer by White.